What happens when you attempt to start the "out of the box" Approval workflow on
a document in a standard document library? If this fails, you may want to start
with restarting the WSS timer and SP Admin services. However, having said that,
I had this problem earlier this week and I was never able to get it resolved.
In addition, I couldn't get any backup jobs to run. I ended up recreating my
virtual development environment. It was quicker for me to do that than mess
around anymore than I already had troubleshooting.
Incidentally, if you're developing in virtual environments, make sure you use
base images and/or snapshots. They'll save you hours, if not days, of time when
something does go wrong (and it will).