You can try to disable hardware acceleration in Firefox.

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"

You need to close and restart Firefox after toggling this setting.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can check if there is an update for your graphics display driver and check for hardware acceleration related issues.

• https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Hi,

I think if you read my original post you will see I've already tried your suggestions.

Greg

It is a problem with some NVidia component (nvwgf2um.dll) and D3D11, so it is definitely related to issues with the graphics display driver.

• Firefox 39.0 Crash Report [@ NDXGI::CDevice::DeallocateCB(void*, _D3DDDICB_DEALLOCATE const*) ]

You can try to toggle the layers.d3d11.disable-warp pref to true on the about:config page.

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) to see if that helps.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/

Changing layers.d3d11.disable-warp pref to true did not help.

Is it strange that this has only recently started to happen. No graphic drivers were updated UNTIL the problem started.

Don't understand why I should boot into safe mode as I don't usually operate the PC in this mode. Please explain?

Greg

Booting Windows in Safe Mode with network support will disable external software, so you can verify that it is indeed a problem with NVidia.

You can check if you have the latest Direct X (D3D) drivers and possibly run the DirectX Diagnostic Tool.

You can try to disable OMTC.

• layers.offmainthreadcomposition.enabled = false

If toggling a pref doesn't help the you can reset the pref to undo/reverse the change.

Hi,

No problem in Safe Mode with Networking.

Disabling layers.offmainthreadcomposition.enabled = false did not help.

Regards,

Greg

Hi,

No other ideas on how to fix this problem?

Regards,

Greg

Create a new profile as a test to check if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Set all plugins to "Ask to Activate" on the "Firefox/Tools > Add-ons > Plugins" page

Hi,

New profile is OK. :)

Have transferred bookmarks and all important information per the link you gave me.

Is it possible to transfer the extensions from one profile to another. I will do one by one and test each as I go?

TIA

Greg