Just thought I'd share a recent experience in the event anyone else was having the same issue...
There are several iPods in my household including a new 2nd Gen Shuffle. About a week ago, I docked it to sync some new songs and ended up leaving it there as I was using my nano for a while and had no reason to remove it. Everything was fine for a few days until (about a week ago) I went to load iTunes and could not get the application to install. I'd get the bouncing beachball and then iTunes Not Responding when I went to Force Quit the app. This happened several times and so I reinstalled iTunes - still had the same problem. Finally, I remembered I still had the shuffle connected to the dock and plugged into the computer (it sits behind my iMac) and when I removed the Shuffle, iTunes loaded perfectly the next time I tried to run it.
Not sure what caused the conflict but thought I'd share...