iTunes could not connect to the iTunes Store.An unknown error occurred (0x80090318)

Hello there, RV47.

The following Knowledge Base article provides information on your exact issue:

iTunes: Possible iTunes Store errors

http://support.apple.com/kb/ts1424

Particularly:

Thanks for reaching out to Apple Support Communities.

Cheers,

Pedro.

If you've already tried reseting your winsock and still the problem persists, you might want to try this. (This solved my problem; maybe it would fix yours, too.) Uninstall iTunes 11 and all the applications that were installed with it. Afterwards, install iTunes 10 instead.

Make sure to delete the library folder created by iTunes 11 in C:\Users\[username]\My Music\iTunes before launching the older versions of iTunes. Otherwise you would receive an error indicating that the programme cannot start.