Direct IMAP connection to the IMAP server (e.g. using Thunderbird, Outlook, or pine) is not affected.
UPDATE
[2009-06-25 09:27:27 | Lars Rohrbach]
Access to the webmail interface to IMAP is working again. The service was restarted a few times during the examination of logs and configuration.
Resolved as of 2009-06-25 09:15:00