I tried to remove the latest version of flash and download one from 8 months ago. Unfortunately this did not help either.

Please try version 3.53.01. You can get it here:

http://www.sandboxie.com/phpbb/viewtopic.php?t=9878

I could not reproduce your problem so this version does not address it specifically, however it addresses enough problems that it might make a difference for you.

I finally found the solution. I recently got a few pop-ups using firefox for some fake pc optimizer, something like that. I knew it was obviously spyware. I tried a lot of spyware programs, with non of them fixing it. I found a website telling someone else with the same problem to use TDSSKiller by Kaspersky Lab. After I ran this it removed the problem. I then thought, maybe I should try sandboxie now. Sanboxie ran FF fine with no problems.

Thanks for everyone for the suggestions and I would recommend that JPjuice23 do the same.

Thanks for the suggestion, but strangely enough Flash asked me to update, and than it worked.

Weird. Oh well, sweet.