One thing for people to try: Please set the following options in xorg.conf:
Option "UseEvents" "False"
Option "DamageEvents" "False"
the second of these requires that the xine window not be redirected, so no compiz for example.
Also note that the first option only affects the X server, not VDPAU's own operation. However, VDPAU uses some of the same operations that X does when the option is enabled, so if the option affects the frequency, that would be useful to know. If there is an effect, knowing which individual option caused it would be useful.