Whenever I try and run iTunes visualizer on a secondary monitor, my entire computer lags extremely badly, as in the mouse no longer moves smoothly, however if I simply drag it over to my primary monitor I receive no issues. I have tried disabling directX and that did not change anything. Its not a refresh rate issue or something along those lines because I can watch full screen video in a variety of different media players on it and not receive any lag. I receive the same problem if I try and watch a video from my iTunes movies library on my second monitor (not on the primary), but its nowhere near as bad, it only is annoying watching video, not unusable like it is with the visualizer.
I have a Radeon X550 if its a problem with the video card.