but to speed up this thread-
there have started to be problems observed with 10.6.4- ( which is why the exact version is necessary )
poor playback/graphics performance in 10.6.4 observed on 4870 but not GT120- so its graphics driver dependant-
there are internet reports of similar things - but i saw it myself last week with a dutch system
http://boardreader.com/thread/Snow_L...2wzX1gvkb.html
Apple is rushing out some graphics driver fix thing - but its not public yet.
Looks like something got broken in 10.6.4