Sometimes the answer is quite simple (sometimes not)
Switched of the Firewall, started iTunes first, and all is good with the world. Why it syncs with my other 2 PC's with the Firewall on, I don't understand, but now I seem to have solved this issue, all is good - for now at least
Thanks everyone for the suggestions and help, I'll go back to my technologically challenged life
with my calendar up to date