Firefox was running without any problems until upgrade to version 3.6. After the upgrade, Firefox will not start. It is aborted during the load sequence, every time. I searched this forum, and did as recommended: Uninstall Firefox. Empty profile folder. Reinstall Firefox. Results: Error message: "Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system." I saved the default profile rueswgfr.default before emptying the profile folder. When I copied rueswgfr.default back to the profile folder, I got the original problem: Firefox aborted during load sequence. (With profile folder, I mean the folder you get when running %APPDATA%\Mozilla\Firefox\Profiles\ from the Start button.) An upgrade to beta 4 did not change anything. Still the same problems.