I just updated from Moodle 1.9 to 2.0 (php version on my server doesn't meet requirements for anything beyond 2.0). In order to complete the process I had to delete the certificate folder from mods. I have tried to add the 2.0 version of certificate, but was getting an error saying that a field already existed. I decided to delete the certificate and certificate_issue tables, hoping this would solve the problem, and assuming that the installation creates the tables for me. Unfortunately, I am now getting an error saying the the certificate table does not exist. The worst thing about the whole process, is that I performed the upgrade for the sole reason of getting the certificate to link to an activity by grade conditional, which was not working properly with the older version, and now it is the only module not installing correctly after the upgrade (several other non-core modules upgraded without a problem).
Any ideas? I did make a backup of the database before upgrading, so I could probably restore the certificate tables if need be.