After using iTunes, my MacBook Pro doesn't shutdown normally.

Download the full itunes 10.5.3 installer and reinstall.

Reboot in Safe Mode (hold down shift after chime), to rebuild caches, reboot again.

If problems persist check /Applications/Utilities/Console note the time of the hang and see if any errors occur at that time.

And most importantly: Don't post your off-topic issue off in other threads.

Just as an FYI, that gray screen is usually the result of a process that is running a loop / can't stop. That's my layman's interpretation of the actual process at least. I believe there were a few issues when Lion came out with that happening for a number of different programs. Search in the general Lion thread for a thread that might be related. FWIW it used to happen to me but doesn't anymore, and all I could suggest is as above (try a full install of iTunes, not via upgrades).

I have the exact same problem with my 2011 Mac mini, but I’ve had it since I bought it (I believe it came with 10.7.2). One question for you: my iTunes Library file is in ~/Music, but the actual song files are on a NAS. How is yours set up?

Oooh… looks like the issue might be with Parallels 7 and Kaspersky Antivirus. Do you have those installed?

https://discussions.apple.com/thread/3428703?answerId=16560483022#16560483022