Whenever I have to log in to a website with a username and password, lsass.exe starts up and locks up Firefox for 30 seconds or so. This only occurs with Firefox, no other browsers. I have already run multiple virus scans as well as 6 or 8 ad/spy/malware scans and everything is clean. To be honest, the performance of Firefox has really gone downhill in the last year. I would really hate to lose it. Is this some sort of add on issue? Is there a security setting that I can turn off?

Any help would be appreciated.