So you are having trouble renewing your OCS 2007 certificate? My certificate expired over the weekend without my noticing and I tried to renew it. Everything I tried was met with some unspecified error through the cert wizard. I tried adding a new CA authority to our domain, adding the RTCServer locally as an administrator, and several other security tweaks. What was the end solution? Opening permissions to everyone on c:\documents and settings\all users. I now have to determine which user actually needs those permissions. Once I made this change everything started working as expected!
Gotta love the lack of error logging on the wizard :)