This morning as I logged onto my work PC, I found that all the extensions/add-ons that I had installed had disappeared. Even the add-ons manager was not responding, though it showed the installed extensions but the controls didn’t work and the window just remained stuck there.
I first suspected the IT support guys to be behind this, they often come up with wierd ideas to restrict a hassle-free browsing environment. But then I doubted their abilities.
A little googling and the problem was solved. The reason was a recent update. And the fix is not that difficult.
First look for your Firefox profiles folder. As this folder could be hidden. To show hidden folders, open Windows Explorer and choose Organize -> Folder and Search Options -> Folder Options -> View (tab) -> Show hidden files and folders.
Delete three files from your profiles folder.
Make sure Firefox is not running when deleting these files. Firefox will regenerate these files on restart.
[All the gyan is from here]