In Firefox 4 and later Safe mode disables extensions and disables hardware acceleration. *http://kb.mozillazine.org/Safe_mode Try to disable hardware acceleration. *Edit > Preferences > Advanced > General > Browsing: "Use hardware acceleration when available" *https://support.mozilla.org/kb/how-do-i-upgrade-my-graphics-drivers ---- Create a new profile as a test to check if your current profile is causing the problems. See "Basic Troubleshooting: Make a new profile": *https://support.mozilla.org/kb/Basic+Troubleshooting#w_8-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, but be careful not to copy corrupted files. See: *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Re-create the profile works. Now everything was OK. Thank you very much