Hi. I recently decided to put my growing iTunes Library on an external HD to save disk space on my iMac. So I copied the whole iTunes Library folder to a 1 TB WD MyBook Essential (USB), and told iTunes to use that library from now on. But now I have real problems and can't find where they come from. When I play music, suddenly the music stops and continues again after some time (mostly about 10 seconds, but sometimes the pause can take as long as a few minutes). Any ideas?