hello, could you go to the firefox menu ≡ > help ? > troubleshooting information, copy the contents of that page and paste them here into a reply on the forum? this might give us a clue what is going on...

{

 "application": {
   "name": "Firefox",
   "version": "46.0",
   "buildID": "20160421124000",
   "userAgent": "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:46.0) Gecko/20100101 Firefox/46.0",
   "safeMode": false,
   "updateChannel": "release",
   "supportURL": "https://support.mozilla.org/1/firefox/46.0/WINNT/en-US/",
   "numTotalWindows": 1,
   "numRemoteWindows": 0,
   "remoteAutoStart": false,
   "autoStartStatus": 2
 },
 "modifiedPreferences": {
   "accessibility.loadedInLastSession": true,
   "accessibility.lastLoadDate": 1461781189,
   "browser.cache.disk.hashstats_reported": 1,
   "browser.cache.frecency_experiment": 1,
   "browser.cache.disk.smart_size.first_run": false,
   "browser.cache.disk.smart_size.use_old_max": false,
   "browser.cache.disk.capacity": 358400,
   "browser.cache.disk.filesystem_reported": 1,
   "browser.download.importedFromSqlite": true,
   "browser.places.smartBookmarksVersion": 7,
   "browser.sessionstore.upgradeBackup.latestBuildID": "20160421124000",
   "browser.startup.homepage_override.buildID": "20160421124000",
   "browser.startup.homepage_override.mstone": "46.0",
   "dom.apps.reset-permissions": true,
   "dom.mozApps.used": true,
   "extensions.lastAppVersion": "46.0",
   "gfx.crash-guard.d3d11layers.appVersion": "46.0",
   "gfx.crash-guard.d3d11layers.feature-d3d11": true,
   "gfx.crash-guard.glcontext.gfx.driver-init.webgl-angle-force-d3d11": false,
   "gfx.crash-guard.glcontext.gfx.driver-init.webgl-angle-force-warp": false,
   "gfx.crash-guard.glcontext.gfx.driver-init.direct3d11-angle": true,
   "gfx.crash-guard.glcontext.gfx.driver-init.webgl-angle": true,
   "gfx.crash-guard.glcontext.gfx.driver-init.webgl-angle-try-d3d11": true,
   "gfx.direct3d.last_used_feature_level_idx": 0,
   "gfx.crash-guard.d3d11layers.feature-d2d": true,
   "gfx.crash-guard.status.glcontext": 2,
   "gfx.crash-guard.d3d11layers.driverVersion": "10.18.10.4276",
   "gfx.crash-guard.d3d11layers.deviceID": "0x0162",
   "gfx.crash-guard.status.d3d9video": 2,
   "gfx.crash-guard.status.d3d11layers": 2,
   "media.gmp-eme-adobe.abi": "x86-msvc-x64",
   "media.gmp-eme-adobe.lastUpdate": 1461781265,
   "media.webrtc.debug.aec_log_dir": "C:\\Users\\Michael\\AppData\\Local\\Temp",
   "media.webrtc.debug.log_file": "C:\\Users\\Michael\\AppData\\Local\\Temp\\WebRTC.log",
   "media.gmp-gmpopenh264.version": "1.5.3",
   "media.gmp-gmpopenh264.lastUpdate": 1461204480,
   "media.hardware-video-decoding.failed": false,
   "media.gmp-eme-adobe.version": "17",
   "media.gmp-gmpopenh264.abi": "x86-msvc-x64",
   "media.gmp-manager.buildID": "20160421124000",
   "media.gmp-manager.lastCheck": 1461974737,
   "network.cookie.prefsMigrated": true,
   "network.predictor.cleaned-up": true,
   "places.database.lastMaintenance": 1462034748,
   "places.history.expiration.transient_current_max_pages": 104858,
   "plugin.importedState": true,
   "plugin.disable_full_page_plugin_for_types": "application/pdf",
   "print.printer_HP_Photosmart_7520_series_(Network).print_edge_right": 0,
   "print.printer_HP_Photosmart_7520_series_(Network).print_unwriteable_margin_bottom": 0,
   "print.printer_HP_Photosmart_7520_series_(Network).print_shrink_to_fit": true,
   "print.printer_HP_Photosmart_7520_series_(Network).print_paper_name": "",
   "print.printer_HP_Photosmart_7520_series_(Network).print_resolution": -437918235,
   "print.printer_HP_Photosmart_7520_series_(Network).print_margin_top": "0.5",
   "print.printer_HP_Photosmart_7520_series_(Network).print_evenpages": true,
   "print.printer_HP_Photosmart_7520_series_(Network).print_bgimages": false,
   "print.printer_HP_Photosmart_7520_series_(Network).print_paper_size_unit": 0,
   "print.printer_HP_Photosmart_7520_series_(Network).print_paper_height": " 11.00",
   "print.printer_HP_Photosmart_7520_series_(Network).print_unwriteable_margin_left": 0,
   "print.printer_HP_Photosmart_7520_series_(Network).print_margin_bottom": "0.5",
   "print.printer_HP_Photosmart_7520_series_(Network).print_to_file": false,
   "print.printer_HP_Photosmart_7520_series_(Network).print_paper_size_type": 0,
   "print.printer_HP_Photosmart_7520_series_(Network).print_reversed": false,
   "print.printer_HP_Photosmart_7520_series_(Network).print_duplex": -437918235,
   "print.printer_HP_Photosmart_7520_series_(Network).print_orientation": 0,
   "print.printer_HP_Photosmart_7520_series_(Network).print_oddpages": true,
   "print.printer_HP_Photosmart_7520_series_(Network).print_margin_left": "0.5",
   "print.printer_HP_Photosmart_7520_series_(Network).print_edge_bottom": 0,
   "print.printer_HP_Photosmart_7520_series_(Network).print_unwriteable_margin_right": 0,
   "print.printer_HP_Photosmart_7520_series_(Network).print_margin_right": "0.5",
   "print.printer_HP_Photosmart_7520_series_(Network).print_in_color": true,
   "print.printer_HP_Photosmart_7520_series_(Network).print_edge_left": 0,
   "print.printer_HP_Photosmart_7520_series_(Network).print_bgcolor": false,
   "print.printer_HP_Photosmart_7520_series_(Network).print_unwriteable_margin_top": 0,
   "print.printer_HP_Photosmart_7520_series_(Network).print_paper_width": "  8.50",
   "print.printer_HP_Photosmart_7520_series_(Network).print_paper_data": 1,
   "print.printer_HP_Photosmart_7520_series_(Network).print_scaling": "  1.00",
   "print.printer_HP_Photosmart_7520_series_(Network).print_page_delay": 50,
   "print.printer_HP_Photosmart_7520_series_(Network).print_edge_top": 0,
   "privacy.sanitize.migrateFx3Prefs": true,
   "privacy.sanitize.migrateClearSavedPwdsOnExit": true,
   "services.sync.declinedEngines": "",
   "services.sync.engine.passwords": false,
   "storage.vacuum.last.places.sqlite": 1461252604,
   "storage.vacuum.last.index": 1
 },
 "lockedPreferences": {},
 "graphics": {
   "numTotalWindows": 1,
   "numAcceleratedWindows": 1,
   "windowLayerManagerType": "Direct3D 11",
   "windowLayerManagerRemote": true,
   "supportsHardwareH264": "Yes",
   "adapterDescription": "Intel(R) HD Graphics 4000",
   "adapterVendorID": "0x8086",
   "adapterDeviceID": "0x0162",
   "adapterSubsysID": "054b1028",
   "adapterRAM": "Unknown",
   "adapterDrivers": "igdumdim64 igd10iumd64 igd10iumd64 igdumdim32 igd10iumd32 igd10iumd32",
   "driverVersion": "10.18.10.4276",
   "driverDate": "8-17-2015",
   "adapterDescription2": "NVIDIA GeForce GT 640M",
   "adapterVendorID2": "0x10de",
   "adapterDeviceID2": "0x0fd2",
   "adapterSubsysID2": "054b1028",
   "adapterRAM2": "2048",
   "adapterDrivers2": "nvd3dumx,nvwgf2umx,nvwgf2umx,nvwgf2umx nvd3dum,nvwgf2um,nvwgf2um,nvwgf2um",
   "driverVersion2": "10.18.13.5362",
   "driverDate2": "7-22-2015",
   "isGPU2Active": false,
   "direct2DEnabled": true,
   "directWriteEnabled": true,
   "directWriteVersion": "10.0.10586.0",
   "webglRenderer": "Google Inc. -- ANGLE (Intel(R) HD Graphics 4000 Direct3D11 vs_5_0 ps_5_0)",
   "info": {
     "AzureCanvasBackend": "direct2d 1.1",
     "AzureSkiaAccelerated": 0,
     "AzureFallbackCanvasBackend": "cairo",
     "AzureContentBackend": "direct2d 1.1"
   }
 },
 "javaScript": {
   "incrementalGCEnabled": true
 },
 "accessibility": {
   "isActive": true,
   "forceDisabled": 0
 },
 "libraryVersions": {
   "NSPR": {
     "minVersion": "4.12",
     "version": "4.12"
   },
   "NSS": {
     "minVersion": "3.22.3 Basic ECC",
     "version": "3.22.3 Basic ECC"
   },
   "NSSUTIL": {
     "minVersion": "3.22.3",
     "version": "3.22.3"
   },
   "NSSSSL": {
     "minVersion": "3.22.3 Basic ECC",
     "version": "3.22.3 Basic ECC"
   },
   "NSSSMIME": {
     "minVersion": "3.22.3 Basic ECC",
     "version": "3.22.3 Basic ECC"
   }
 },
 "userJS": {
   "exists": false
 },
 "crashes": {
   "submitted": [],
   "pending": 0
 },
 "extensions": [
   {
     "name": "Firefox Hello",
     "version": "1.2.6",
     "isActive": true,
     "id": "loop@mozilla.org"
   },
   {
     "name": "Multi-process staged rollout",
     "version": "1.0",
     "isActive": true,
     "id": "e10srollout@mozilla.org"
   },
   {
     "name": "Pocket",
     "version": "1.0",
     "isActive": true,
     "id": "firefox@getpocket.com"
   },
   {
     "name": "Trend Micro BEP Firefox Extension",
     "version": "9.1.0.1035",
     "isActive": false,
     "id": "tmbepff@trendmicro.com"
   },
   {
     "name": "Trend Micro Osprey Firefox Extension",
     "version": "2.0.0.1083",
     "isActive": false,
     "id": "{BBB77B49-9FF4-4d5c-8FE2-92B1D6CD696C}"
   },
   {
     "name": "Trend Micro Toolbar",
     "version": "9.0.0.1256",
     "isActive": false,
     "id": "{22181a4d-af90-4ca3-a569-faed9118d6bc}"
   }
 ],
 "experiments": []

}

thank you, nothing obvious is showing up there unfortunately. could you try a clean reinstall of firefox?:

• download full firefox setup file from getfirefox.com
• uninstall firefox on the machine
• manually delete all remaining files in the firefox program folder, which usually resides in C:\Program Files (x86)\Mozilla Firefox\
• reinstall firefox

Thanks for the reply, but a complete re-install is a bit too much. I can live with the issue for now.

this won't affect your settings or customisations but would just make sure that there are no unintended additions to the firefox installation directory...

Thanks again

i've learned from other users that the trend micro password manager might be responsible for that behaviour as well. please uninstall it through your system control panel in case you're not using it.

I do have Trend Micro running on my machine, but I'm not using the password manager feature. Could this still be the issue?

Yes, I think it's interfering this way as soon as it's installed on a system. I'd remove it if you don't make use of it.

I deleted the password manager for trend micro and it appears that the problem is solved. Thanks for your help