unkillable processes

[Paul]

There's a situation I've seen a few times now, with assorted programs,
though most often with explorer. It occurs when a process tries to spawn a
child process.
The spawn seems to fail and the would-be parent hangs ... except it hangs
in a way that means it can't be killed. The killing (whether through task
manager or taskkill -f) claims to be successful, and yet nothing happens. I
am left with a window frozen on my desktop I can't remove. At this point I
can't log out, stuff just starts to hang if I try.

Oddly I have a suspicion putting the machine into hibernation and back
makes it go away.

Has anyone seen this before?

Thanks,

Paul