No new messages on Mac Mail with iCloud
My Mavericks Mail.app has stopped receiving and displaying new messages for my iCloud account. I can view new messages via the iCloud web interface. Sending mail from my client works fine.
I have tried disabling/re-enabling the account from both the Mail -> Accounts menu and the System Preferences -> iCloud menus. In both cases, the account returns with the same message list (last message received on 12/21).
Any thoughts or advice?
Thanks in advance
MacBook Air, OS X Mavericks (10.9.1)