Reset messed up certificate data in Firefox and Thunderbird?

Solution 1:

I looked up your error in regards to Firefox, and found this solution:

1. Type the phrase about:support as a URL in the Firefox address bar.
2. Click the button next to Profile Directory labeled "Open Containing Folder". That will launch Windows Explorer.
3. Close Firefox.
4. Locate the file cert8.db in the Windows Explorer pane you opened in step 2 and move the file to a different location (like your desktop) or rename it.
5. Start Firefox again.

This will clear the file out and should resolve the errors you are getting.

Solution 2:

For Thunderbird, you can click on Help then Troubleshooting information. Then click Show Folder next to Profile Folder. Just right click and rename the cert8.db, or cert8, to cert8ORIG. Then reopen TB. You might have to accept certificate exceptions for some mail services, but it will remember them for the future.