i don't have quite the same issue but from the sound of it, it's somewhat similar. For me, iTunes hangs whenever I have it open (whether there's music playing or not), I go to another application like Safari, a Newsreader, Lightroom (any app really) and then come back to iTunes after a while. Once the iTunes window gets focus, there's a brief second of pause and then the spinning beachball comes on. I have to force quit it to be able to use it again. - I've tried restarting and that seemed to alleviate the issue, at least for a while. Today it's back again though, so that didn't work. Also saw someone suggesting to turn off any store and iTunes Music related stuff but that didn't work for me at all.
So yeah, if anyone has an idea, please post! TIA!