Recently I discovered iTunes was not starting up on my Windows 7 machine. I was pretty mystified – it worked with my other user account, yet even after I closed all applications and stopped services, and reinstalled all Apple applicaitons, I still had the same problem on my primary user account. I eventually noticed that when I unplugged my network, it started working! I investigated further with Wireshark to determine what iTunes was doing on the network to make it hang and found this:
19 1.947615 192.168.2.105 192.168.2.119 SMB 302 Session Setup AndX Request, User: dcoetzee-dv8t\dcoetzee; Tree Connect AndX, Path: \\192.168.2.119\RAID
Sure enough, my FreeNAS RAID had gotten itself into a bad state and was hanging whenever an attempt was made to contact it over SMB/Windows File Sharing. Apparently unbeknownst to me, iTunes scans mapped network drives at startup. I rebooted the RAID and the problem went away.