M, I think I found the answer. I have Backup Exec installed on a different server than my Exchange Server so I have the remote agent installed on the Exchange Server. While looking in the Event Viewer during the Rollup 4 uninstall, it appeared that the remote agent, beremote.exe, was preventing the uninstaller from accessing certain Exchange files. Once I stopped and disabled the BE 12 services on the Exchange server, the uninstall worked perfectly. In fact, I didn't even have to modify the web.config file. After a reboot, I ran the Rollup 3 (Exchange2007-KB949870-x64-EN.msp), reset the BE 12 services to automatic, and rebooted one last time. I just ran a full exchange backup and all of the errors went away.