iTunes & Vista - UI "freezes"

Can anyone point me in the right direction of trying to resolve an issue with itunes where the UI locks up? For a little while, iTunes works fine and then the graphics get distorted, I lose the menu bar and if you try to minimize and restore the app, it doesn't do anything. The app is still running, tunes are playing but something it up with the UI.

Any idea what is going on?

Thanks
Mark