Firefox is rejecting too many certificates that (ugh) IE accepts.
I've been having this problem of rejecting certificates because the issuer is not recognized. I have it on Firefox 5.0.1. I had it on 5.0. But IE works fine. The listed URL is just one of many. But most sites do work so it is just certain certificate issuers.
Wšykne wótegrona (3)
Check the date and time in the clock on your computer: (double) click the clock icon on the Windows Taskbar.
The date and time are accurate. They would also affect IE if they were wrong. I figure that the certificate list in Firefox must be out of date even though I just installed 5.0.1 and should have gotten a new list. If not, is there any way to get a fresh copy of the certificate list?
Rename the file cert8.db to cert8.db.old in the Firefox Profile Folder to remove all intermediate certificates that Firefox has stored by visiting secure websites.
If that helped to solve the problem then you can remove the renamed file cert8.db.old unless you have user certificates that you may want to export first and import them in the new file.
Otherwise you can restore the certificates by renaming (copying) the file back to cert8.db