H.264 won't play with my ATI 9200 vid card

i have quicktime 7 installed on my B&W 400 MHz G3. when the original 16
MB ATI card was in place the new video trailers in the H.264 codec
played fine, no problem.

Now that i have the new ATI 128 MB 9200 Mac Edition card in place the
H.264 vids won't play. sound is good, and there is the occasional still
frame, but otherwise a black screen in the vid area.

All other vids play as normal and the card functions fine. any ideas?

Jim