POP3 working, IMAP is not

[patrick]

I have a Cyrus IMAP 2.2.13 server running, and all of the sudden IMAP
connections are not working properly. Users connecting via our webmail
(Horde/IMP) don't see any messages and it says it can't retrieve the
quota. If I connect via POP3 I do, however, see all of the messages
there. I tried connecting via IMAP from a desktop client
(Thunderbird), and it is showing me *most* of the messages, though not
any from today. I've scoured the logs, but don't see any errors.

Has anyone ever experienced this?

Patrick