sudo add-apt-repository ppa:mozillateam/firefox-stable
   sudo apt-get update
   sudo apt-get upgrade

I recently upgraded to Firefox 4 on ubuntu 10.04. I did this by setting the ppa as described in many places: For example: sudo add-apt-repository ppa:mozillateam/firefox-stable sudo apt-get update sudo apt-get upgrade After doing this, firefox has been working for many days just fine. On several of my systems [ 3 of my systems ]. Now I come back to one of my 10.04 systems and find that the menus of firefox are unresponsive. They do not work at all. The book marks do not work. Processor is not busy. Plenty of memory. Network is working fine. If I type into the google search bar and type enter I get a page and I can navigate from there, but the menus and bookmarks are totally unresponsive. What gives? I have rebooted the system and nothing changes. Menus work fine in other apps, for example System Monitor. and the Window Manager menus are fine. Menus work fine in the web pages. Bookmark menus highlight, they do not pull down. Menus on the menu bar do not pull down. Toolbar buttons work fine.