See: * http://kb.mozillazine.org/Firefox_crashes * https://support.mozilla.com/kb/Firefox+crashes ----- Start Firefox in <u>[[Safe Mode]]</u> to check if one of the extensions is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes). * Don't make any changes on the Safe mode start window. * https://support.mozilla.com/kb/Safe+Mode * https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes

hello, thanks for your reply. it stops working in safe mode too.

You can try to do a clean reinstall. Download a fresh Firefox copy and save the file to the desktop. * Firefox 5.0.x: http://www.mozilla.com/en-US/firefox/all.html * Uninstall your current Firefox version. * Do not remove personal data when you uninstall the current version. Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer. * It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling. Your bookmarks and other profile data are stored elsewhere in the [http://kb.mozillazine.org/Profile_folder_-_Firefox Firefox Profile Folder] and won't be affected by a reinstall, but make sure that you do not select to remove personal data if you uninstall Firefox. ---- Create a new profile as a test to check if your current profile is causing the problems. See: * [https://support.mozilla.com/kb/Basic+Troubleshooting#w_8-make-a-new-profile Basic Troubleshooting: Make a new profile] There may be extensions and plugins installed by default in a new profile, so check that in "Tools > Add-ons > Extensions & Plugins" in case there are still problems. If that new profile works then you can transfer some files from the old profile to that new profile (be careful not to copy corrupted files) See: * http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox