itunes problem

Don't know if anyone can help, but in itunes, when I click 'add a song or file' and the folder browser window pops up, usually if you click outside a beep sound is made as you can only click in the browser window.
However in itunes when i do this, or even if i leave it for more than a few seconds the pop up browser window vanishes and when i click it flashes up for a second then dissapears, with the usual beeping noises. It's as if its dissapearing behind the itunes window. Tried reinstalling itunes but didn't help. Wonderind if anyone had any ideas as to what to do?
thanks