I recently had a problem with Data Protection Manager and the "Consolidation of recovery points." The problem was actually with the VSS service on the computer being backed up but the recommended action in DPM was to allocate more disk space for shadow copy. When I attempted to do this I was confronted with this error:

The operation failed because of a protection agent failure.Retry the operation.ID: 998Details: Unknown error (0x80042318) (0x80042318)

I couldn't find much on the Internet concerning this error so I logged into the client machine (the one being backed up) and checked the VSS service. Sure enough, it was in a Stopping state. I couldn't kill the service with tskill so I grabbed an old kill.exe program in my toolkit and blew it away (as a side note, I don't know who created the kill.exe app that I use but it is very handy. If you would like a copy, send me an email and I will send get it to you).

After killing the service, I ran Synchronization job with consistency check using DPM and all was good.