I suggest installing Firefox 3.6.18 and, if necessary, creating a new blank Firefox profile.

First, I recommend backing up your Firefox settings in case something goes wrong. See Backing up your information. (You can copy your entire Firefox profile folder somewhere outside of the Mozilla folder.)

Next, download and save Firefox 3.6 to your desktop for future installation. http://www.mozilla.com/firefox/all-older

Close Firefox and install 3.6.

Try Firefox. Does it work normally?

If not, close Firefox and fire up the profile manager. Click the Windows 7 start "orb" and type or paste the following into the search box and press Enter:

firefox.exe /ProfileManager

Create a new profile, which will be more or less plain vanilla. To move key settings like bookmarks from your problem profile to the new profile, see: Recovering important data from an old profile.

Hope this helps.

Works like charm ! How can I delete my old profile ? Just for security purpose.

How can I delete my old profile ? Just for security purpose.

For the one in the Mozilla folder, you can delete it using the profile manager. This probably bypasses the recycle bin, so if you made a backup, you might hang onto it for a bit.