iTunes download error 404 - support issue

I'm at my wits end after getting an 404 error message after purchasing music via iTunes but being unable to download it. It says the url cannot be found on the server.

The really frustrating thing is that none of the online support documents cover my problem. I have repaired permissions, rebooted, re-installed iTunes 7 and tried to install it on my other mac, all with the same error message.

How do I contact the iTunes online support guys as there appears to be no obvious link via iTunes or the support pages?

I'm not going to be a happy bunny if I get charged for music I can't download.