Some of our client applications use Thawte SSL certificates. We've used them for year without any problems.
Recently Thawte upgraded their root certificate paths to make them deeper.
When we went to install the certificates on ISA server, we started getting error messages in the browser that the certificate chain had issues.
We found the relevant support article at Thawte and made sure all of the intermediate certificate authorities were installed, etc.
Still the problem persisted.
Resetting the publishing rule didn't work either. The certificates were there and everything was configured as per the specifications.
Only one option remained.
Reboot the server.
It used to be the first thing an IT person tried when something was not working. But in 2010 we expect to be able to reconfigure most things without a reboot.
But even today, when all else fails, reboot.