CalDAV syncing woth google calendar has just stopped working..

Looking in accounts, the CalDAV account now says its never been synced (i know it has, since i can see some google calander entries, but nothing that ive aded since yesterday).
I cannot syc it even by pressing the Sync button.

After deleting the accoutn and trying to add it again, I get this message:
"You can't use Calendar in this service right now. Please turn on service Calendar on first and try again."

Ive tried creating the account whilst on 3G and wifi