When I try to check the shadow storage usage on my system using "vssadmin list shadowstorage", I get an error returned:

Error: The shadow copy provider had an unexpected error while trying to process the specified command.

and in the event viewer I'm seeing the message:

Volume Shadow Copy Service error: Error calling a routine on a Shadow Copy Provider {b5946137-7b9f-4925-af80-51abd60b20d5}. Routine details IVssSnapshotProvider::QueryVolumesSupportedForSnapshots(ProviderId,-1,...) [hr = 0x8000ffff].

Operation:
   Query volumes supported by this provider

Context:
   Provider ID: {b5946137-7b9f-4925-af80-51abd60b20d5}
   Snapshot Context: -1

Does anyone have an idea of what this means? Any way to fix it?

I'm using Vista Ultimate 64 bit.

Hmm - that's a very uncommon return value for the vssadmin tool, especially on the Microsoft VSS provider GUID (the win32 failure code is E_UNEXPECTED, catasrophic failure). I'd say to uninstall any antivirus/antispyware/backup applications on the machine, including any volume mounting utilities (like daemon tools, for example), and see if the problem continues after a reboot.

Wow, I'm always amazed at the skill on this site . I removed Daemon Tools, rebooted, and everything worked fine. Then, as a control, I installed daemon tools again. Right after it installed SPTD, vssadmin started giving me trouble again.

At least I know who to blame now.

Thanks a lot cluberti