Widnows freezes after I close a game...?

Hey,

This had just started hapenning to me... Every time I close a game like WoW or CS:S the game will close and my desktop will come up but I wont be able to do anything... If I click an icon to launch something nothing happens, if I try to opent the start menu nothing happens. I can't do anything except look at it...

If I had music playing in game from winamp or something it will comntinue to play even though windows seems to be frozen...

Any ideas on why this is happening and how I could fix it?

Thanks