I used to have this kind of ****. I was on integrated Gfx back then, so I doubt it's your card. I'd go with t3ice and say change and/or test your memory rather extensively.
Also, do the normal kind of stuff: update drivers, if you recently HAVE updated drivers then roll back, update DX9/10 if you see fit, just the general kind of trouble shooting stuff... Until then I guess you should probably just try to avoid Alt+Tab-ing. Try buying a cheap Multimedia Keyboard so you won't have to minimize the window to change songs.
Actually, you may want to buy a nice multimedia keyboard, because you will get very addicted to being able to change songs at the push of a button. Miss 'em on this new board. =(