I am having the same issue I posted this elsewhere
I have a Mid 2010 Mac Mini Server (full specs below) and very recently it has developed a strange problem. I'll be watching something on iTunes and the video will stop but the audio continues. If I move the mouse and click on the screen the video suddenly plays very fast untill it catches up with the audio and then for a while it will play normally. I can go through this process 3-4 times an hour before I give up and stream to my iPad instead.
in the beginning it only happened when I was using the HDMI cable but recently it happens when the mini VGA adaptor is plugged in too.
its beginning to be very frustrating so any help would be truly appreciated.
thanks
James
Mac Mini Specs
Intel Core 2 Duo 2.66 Ghz
8GB Ram
Running Lion Server 10.7.2 (111C74)
ITunes 10.5.2