Happens on my AMD64 3800 as well.
I also had the problem of the 5.0 drivers dropping frames in 24p mode when I used Sony Vegas 6.0. It was almost like the decklink SP card was not applying the pulldown. Once I switched back to BM 4.8.1, the problems went away.
dolby
Motherboard Gigabyte GA-K8N Ultra-9
Video Nvidia 6200 PCI-X
Windows XP SP2
Directx 9c
Quicktime 7