iTunes messing up for some reason, after update

I updated to iTunes6 the other day and now I have been having problems, whenever I try to play music, my screen goes black, but songs play and if I click the mouse the screen comes back. Plus I noticed if I take a screen shot of visualizer the image is created smaller than the screensize
Screen size is 1680X1050 and it comes up 640X480 is there a setting that's off? I checked itunes pref., it's set for full screen Any ideas?