password verification failure

[Michael Jørgensen]

This must really be a neewbie problem .-(

I'm trying to connect to my IMAP server using Thunderbird. I'm not 
interested in SSL, so in Thunderbird I selected the radio button "TLS, 
if possible". However, Thunderbird refuses to talk to the IMAP server, 
and disconnects immediately after receiving the initial greeting from 
the IMAP server.

Then I tried running IMAP over SSL and selected the radio button "SSL" 
in Thunderbird. Now it asks for my username and password, and then 
fails! In the file /var/log/maillog I see the lines:
Feb  2 20:44:40 mij-6 imaps[5690]: badlogin: [10.0.0.105] plain 
[SASL(-1): generic failure: Password verification failed]
Feb  2 20:44:43 mij-6 imaps[5690]: badlogin: [10.0.0.105] plaintext mij 
SASL(-1): generic failure: checkpass failed

The file /etc/imapd.conf contains the following lines:
configdirectory: /var/lib/imap
partition-default: /var/spool/imap
admins: cyrus
sievedir: /var/lib/imap/sieve
sendmail: /usr/sbin/sendmail
hashimapspool: true
sasl_pwcheck_method: saslauthd
sasl_mech_list: PLAIN
tls_cert_file: /etc/pki/cyrus-imapd/cyrus-imapd.pem
tls_key_file: /etc/pki/cyrus-imapd/cyrus-imapd.pem
tls_ca_file: /etc/pki/tls/certs/ca-bundle.crt

I'm running the latest Fedora Core, the version of the IMAP server is 
cyrus-imapd-2.3.9-7.fc8. Any help is greatly appreciated.