"iTunes can't verify the identity of the server "ax.itunes.apple.com".

Followed by the usual certificate expired blah blah. Using iTunes 10.2.1

If I hit cancel, everything is fine.

I don't know if the latest upgrade sneaked past me with another software upgrade, but I never upgrade iTunes because it tells me to. That starts the cycle of having to upgrade everything until you need a newer computer. Upgrading iTunes is a sinkhole, and it took me a long time to realize it and why they do it.