After doing what I described in the thread title, Firefox 4 presented the following issues: 1- Tabs would not close. 2- The "forward" and "back" button would not be lit or clickable, as if I didn't visit any websites. Although pages did load, I could not go back and forth between them via these buttons. 3- the "feedback" button in the right-hand side of the screen was completely gone. Trying to download the respective feedback app that Mozilla provides didn't work, it wouldn't download. 4- the App Management screen would not open. 5- I did not save any of the pages from the previous session. So I closed FF 4 and opened 3.6 once again (wich appears to be functioning normally) and the pages came back So basically my FF 4 got completely messed up. Reinstalling it did nothing. Cleaning the registry with Registry Mechanic was to no avail either. I had to uninstall FF4 since it was unusable. Possibly useful fact: The apps I had removed in FF 4 were also removed in 3.6, wich indicates that maybe the FF 4 installation did not create copies of it's own for the bookmarks, apps, cache etc, so I am afraid to delete those when the FF 4 uninstallation wizard prompts me to, as it would also probably delete the stuff I have in 3.6 . == This happened == Every time Firefox opened == Started after using Firefox 3.6 then switching to 4 again.