Sorry for bumping this thread, but it seems Google CalDav is no more available.
After I've changed the password for my google account, CalDav on my N9 stopped syncing and started asking for a new password. I tried entering it several times, but had no success, though I'm sure it was typed correctly; then I deleted the CalDav from Accounts. Now, when I'm trying to add new caldav acc, fill in all the fields, and press 'Sign in' it says:
"You can't use calendar in this device right now. Please turn service calendar on first and try again"

Any thoughts? Anyone can confirm this?