Upgrade from debian squeeze to wheezy / problems with "umlauts" in mysql logging

[Bastian via amavis-users]

Hi there,
today i did an upgrade from squeeze to wheezy, resultin in an amavis
update to version 2.7.1-2, and mysql is now 5.5.
I am logging amavis mails to mysql, but after the update, german umlauts
look like this:

mysql> select subject from amavis.msgs where subject like "%und fusionen%" ;
+----------------------------------------------------------------+
| subject |
+----------------------------------------------------------------+
| Übernahmen und Fusionen - Schäppchenjagd für Anleger? |
| Übernahmen und Fusionen - Schäppchenjagd für Anleger? |
+----------------------------------------------------------------+
2 rows in set (0.01 sec)

The second mail was logged before the update. Can someone please give me
a hint what the problem could be,
and if it is related to amavis, how to resolve this? The DB collation
did not change.

Thank you,
Bastian