jittery playback when ui is hidden.

when ever i play a video, it plays fine until the ui hides and instantly it starts to jitter and will continue to do so. when it is playing with the interface, it plays smoothly for however long i keep it up. any ideas?
i’m streaming over the network. local playback was fine. i’ve also modified the advanced settings to fill at a rate of 10 with 400MB of cache. (changing these settings seams to have no effect..)