ITunes "can't connect to the CDDB server" for tracks on a CD (but can once I've imported them)

Question

When I insert a CD into my computer, iTunes cannot get the track names before importing, I get the "Unable to connect to the CDDB server. The network cannot be reached." Bizarrely, however, once I import the tracks onto my PC and ask iTunes to 'Get Track Names' for the files in my library, it can do it fine. I am also able to access the iTunes Store without trouble.
Also, in what I'm sure is related, the Apple Software Update program does not work anymore ("The server could not be found"), so I've to manually download new versions of iTunes from the Apple website.
I've had this problem for months, and I've tried pretty much every solution I'd seen posted for similar problems (reinstalling iTunes, disabling my virus protection, updating Gracenote, ensuring the proxy settings are automatic) with no success.

Answer 1

I've just tried putting my computer into Safe Mode (with netwroking) to check if there was some other program stopping it from working properly, but iTunes still acted the same. It's more of a minor inconvienience than a problem, seeing as I can just get track names after importing and update manually, but it's still pretty baffling.