Sorry - that command isn't solving the issue for me. Thanks nevertheless...
When peeking in the maillog I see:
May 21 17:43:49 ws02 imapd: Connection, ip=[127.0.0.1]
May 21 17:43:49 ws02 imapd: IMAP connect from @ [127.0.0.1]INFO: LOGIN, user=prueba, ip=[127.0.0.1], protocol=IMAP
May 21 17:43:49 ws02 imapd: Connection, ip=[127.0.0.1]
May 21 17:43:49 ws02 imapd: IMAP connect from @ [127.0.0.1]INFO: LOGIN, user=prueba, ip=[127.0.0.1], protocol=IMAP
May 21 17:43:49 ws02 imapd: 1148251429.491377 LOGOUT, user=prueba, ip=[127.0.0.1], headers=0, body=0, rcvd=96, sent=468, maildir=/var/qmail/mailnames/apice.com.co/prueba/Maildir
May 21 17:43:49 ws02 imapd: /etc/courier-imap/shared/index: No such file or directory
The important being the last line: a not found file.
Any hints?