Rather difficult to say what the problem may be at present but for general info please have a look at * [[safe mode]] *[[firefox will not start]] *[[firefox hangs]] Note sometimes you may have to wait a while for firefox to shutdown completly, and if it has hung then as explained in the above articles you may need to kill any firefox.exe process that is still running (and maybe plugincontainer.exe) Try starting firefox in [[safe mode]] e.g. by holding down shift key * do not make any changes in the first window, just click on continue<br/> ? Do you get as far as seeing the options window for safe mode ? If firefox is crashing see [[firefox crashes]], this is easier to work through if you can get firefox to start without crashing on startup. Currently some firefox users are finding Firefox 10 crashes on startup, and a new version Firefox 10.0.1 is being released very soon to deal with this and another cause of hangs. ------------------ Not saying any of this applies to your case but recent issues include * ask tool bar causing hangs if video is used none English versions [/forums/contributors/708073] * possibly some crashes do not start the crash reporter and other issues [/forums/contributors/708122?page=2#post-45059] * some general info about current crashes [/questions/917748#answer-308124]