I think if you reread my post you will see that it is not at all a resource thing.. its OS related. I have tested this quite a bit. It makes no difference how many videos I am playing or of what size. basically if you are running a couple layers of stuff in cat and then enable say a few lfg inputs... and dont even assign them to a layer... the GPU usage will become very unstable and periodically go through bouts of huge spikes for a few seconds causing frame drops etc... this can happen while only using a small percentage of available gpu. This is ONLY IN SNOW LEOPARD.... if I play the exact same videos and turn on the inputs on the same machine in LEOPARD this problem no longer exists... it will run perfectly stable. To satisfy your question about my system:

late 2008 octo core 3.2ghz macpro
8GB ram
8800gt gpu
m257
intel X25mG2 160gb ssd

Once again this happens in instances where playback is in no way demanding on the machine. I have now encountered this on my machines and others.