User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:7.0.1) Gecko/20100101 Firefox/7.0.1 Build ID: 20110928134238 Steps to reproduce: - Installed FF on Win7 x64 - installed some addons (see attachment) - selected a menu, from menu bar, context, addon or else - try to move mouse to desired item Actual results: On mouse movement, the menu diappears, thereby making the underlying content visible. Moving the mouse further, the menut shortly flickers, but mostly remains invisible. The menu items - if you know where they are - are still in charge ... clicking on the correct spot works. Does not happen all the time (nut often), and even an invisible or flickering menu may settle back to normal. Expected results: Classic menu behaviour ...

Sounds like a duplicate of bug 679287. Sebastian

As of bug 800701 this was fixed back in the beginning of 2013. If this bug still occurs, please re-open that bug or file a new bug as appropriate. Sebastian