Problems shutting down

I'm running activated RC1, and was totally impressed with the speed
improvements over Beta 2. For some reason though, it's now taking over 10
minutes to shut down and last night it automatically rebooted to a screen
similar to the old dual-boot screen saying that Windows didn't shut down
properly and suggested starting in safe mode. I let it boot normally and the
error reporting popup appeared but after checking it just closed, not even
saying there is no current fix and to check back later. It's about the 5th
time the slow shut-down has occurred, but the first that it didn't shut down
at all and rebooted.

I'm wondering if PC-Cillin has anything to do with it. does anyone know of
any other anti-virus programs with demos that will run on Vista? Anyone else
having shut-down problems?