Rename (or delete) the file cert8.db (cert8.db.old) in the Profile Folder to remove all intermediate certificates that Firefox has stored by visiting secure websites.

Help > Troubleshooting Information > Profile Directory: Open Containing Folder

I had just figured this out when I got your reply. Actually, I first did the part you mentioned, and then extracted a two month old cert8.db file from a Norton Systemworks backup and placed it into the folder.

In fact, there are two instances of cert8.db in the Docs and Settings folders - one is apparently an original, dated years ago, and the other is the updated one, which is the one I replaced. Now I get no notices of bad certs.

However, my copy of Invisible Hand 3.2 apparently still doesn't work - it shows up in the lower right corner, but doesn't activate. Oh well, that's another problem for another day....

Anyhow, thanks for your help - you had the right answer. I would just add that an older, known good version of the cert8.db file should be substituted for the corrupt one, if one wants to preserve certificates already loaded.

Thanks, airpilot

You can do restore an older of cert8.db to keep other saved (intermediate) certificates.

If you know which certificate(s) cause the problem then you can remove them in the certificate manager.

• Tools > Options > Advanced > Encryption: Certificates > View Certificates : Authorities

Intermediate certificates that were added by Firefox after visiting a website are listed as "Software Security Device".