First I tried the manual backup of WMI to the WBEM\Repository, and it went fine.
I tried what W. Yauch suggested, registered the DLLs, went into the properties for the WMI service and set it from "automatic" to "disabled", then stopped it. I then tried to rename the WBEM folder, but got a sharing violation. Rather than take down the server, I restarted the WMI servce and set it back to "automatic". I then went into the Symantec AV 10.0.2 and excluded the WBEM folder from autoprotect. This morning, I got a call that the backup ran fine! It had failed twice in a row, after installing SAV 10, loading all the Win2k Critical Updates and MS AntiSpyware.
Whether this was fixed by re-registering the DLLs or excluding the WBEM folder, I do not know. Neither have I had a chance to run it cleanly more than once. (A manual backup DID run to completion, but the 2 scheduled backups failed.) The previous antivirus was InnoculateIT 6. I am using BE ver 9.0, from what I can tell, upgrading to 9.1 would not have helped any.
Thanks for posting suggestions on this thread, you guys have been more help than the Symantec technicians!