IMAP problems

["Karl-Heinz Schulz" <karlheinz khschulz com>]

I experience all of the sudden problems with IMAP.  It is not possible to
download my pop mail.
When I telnet into the server and using "mail" I can see lots of messages.
When using something like pine or Netscape I get the messages "no mail on
the server".
It used to work until a week and I made no changes.

Where can I start to fix/find the problem?

Thank you