postfix won't accept my password anymore

[k4tfish]

Hi, my postfix won't accept passwords using StartTLS since some days.
Plaintext logins are still possible. The deamon produces the following err msg.

Feb 21 00:48:33 reniced postfix/smtpd[9711]: connect from unknown[176.6.x]
Feb 21 00:48:34 reniced postfix/smtpd[9711]: warning: SASL authentication failure: Password verification failed
Feb 21 00:48:34 reniced postfix/smtpd[9711]: warning: unknown[176.6.x]: SASL PLAIN authentication failed: authentication failure
Feb 21 00:48:35 reniced postfix/smtpd[9711]: warning: unknown[176.6.x]: SASL LOGIN authentication failed: authentication failure

The only change on the server are i made are package upgrades.

[UPGRADE] linux-base 2.6.32-46 -> 2.6.32-47
[UPGRADE] linux-image-2.6.32-5-amd64 2.6.32-46 -> 2.6.32-47
[UPGRADE] linux-libc-dev 2.6.32-46 -> 2.6.32-47

What could happen? Thx inadvance !!

k4tfish