Hi all,
After installing 10.5.1, I also lost my connection to iTunes store. All other network connections (internet, mail, software update...) seemed to work fine... After much fiddling about, I tried deactivating "stealth mode" in the Firewall options, and bingo, I can connect again.
I turned Stealth Mode on myself, so if you've never done this, then my advice might not help, but in any case, that was definitely what was blocking my access...
Incidentally, while fiddling, I also noticed something weird happening with my Logitech Mouse driver whenever iTunes launched, and I discovered a keychain issue — redundant X509 Certificates, and two references to the System keychain files ?? — both of which I fixed. Running Disk Utility then showed up serious disk errors, which I fixed as well, but none of that had any effect on the iTunes issue...
Hope this helps!
Message was edited by: Colin Harrison