This isn’t to say that life is roses now. Vista is still slow and seems to get slower (to the point of being almost unresponsive) under relatively light loads. But it recovers now and it never did.
So the next question is, what caused this process’s CPU and memory consumption to render the system unavailable, and why did it go haywire in the first place? I don’t know the answer to the second question, but I can only suspect that there’s something in my list of offline files that caused the service to start killing my system. I’ll try purging the list and reactivating the feature to see what happens.
But the other question: I’m pretty sure that the unresponsiveness has to do with the fact that CSCService was running in the same process space with half a dozen other services, including the window manager. Bad, bad, bad, bad, bad, as Juliette Lewis said in Natural Born Killers. I think I read something about changing the affinity setting for svchost processes in the registry to prevent this behavior; that might be the other thing worth trying to get the feature working again.
For now, I’m just happy that the perp has been fingered.