Vista - Boot critical file is corrupt: ...\drivers\ecache.sys

I've been using 5384 since it's release, quite happily. Not had a single
problem with it, other than the usual beta type issues. Until...

I was using my 2nd machine, Vista went to the screensaver, so I moved the mouse
to get it back. It had hung. I left it in that state for 10 mins to see if it
would come back, but it was completely dead. Having powered the machine off
and back on, I receive the following error at boot:

Boot critical file c:\windows\system32\drivers\ecache.sys is corrupt.

Fair enough, I figured powering it off probably caused that as nothing was
running on the machine at the time.

Here's the problem. You cannot restore that file. It's a boot critical file,
but there's no copy of it in the driver store or system volume information.
Booting from the Vista DVD and selecting Startup Repair also fails after
starting the repair because the file is missing.

What's worse, is it doesn't exist on the DVD either.