[SOLVED]Firefox is already running.

I have an issure running Firefox 3.6 (Upgrading to 4.0 didn't help) where whenever I try to run Firefox, even if it is the first time since the computer has been on, I get the error message "Firefox is already running but is not responding. To open a new window you must end the process or restart your computer." I checked Task Manager but firefox.exe is not running. Restarting does not help, I have also reinstalled multiple times and installed in different folder and harddrives but to no avail. I scanned the Firefox install folder with avast! but found nothing. I have not been able to find any fixes to this problem.
Thanks in advance.

Edit: Making a new profile fixed it!