ProgrammingError - invalid byte sequence for encoding "UTF8"

Dear list members

I have 2 Zope servers (Zope 2.10.5, Python 2.4.4) on 2 physically 
separated machines. Both Zope servers access the same PostgreSQL (8.2.0) 
database on a remote server.

   Zope Server #1 has installed "psycopg2-2.0.5.1".
   Zope Server #2 has installed "psycopg2-2.0.6".

The Data.fs of both Zope Server #1 and #2 is the same.

On Zope Server #2, if I use a ZSQL Method to query the PostgreSQL 
database with umlauts (e.g. "lär") I get the following error:
On Zope Server #1 with installed "psycopg2-2.0.5.1" everything works fine.

Error Type: ProgrammingError
Error Value: invalid byte sequence for encoding "UTF8": 0xe47225 HINT: 
This error can also happen if the byte sequence does not match the 
encoding expected by the server, which is controlled by "client_encoding".

Traceback (innermost last):

     * Module ZPublisher.Publish, line 119, in publish
     * Module ZPublisher.mapply, line 88, in mapply
     * Module ZPublisher.Publish, line 42, in call_object
     * Module Shared.DC.ZRDB.DA, line 343, in manage_test
     * Module Shared.DC.ZRDB.DA, line 321, in manage_test
     * Module Shared.DC.ZRDB.DA, line 500, in __call__
       <SQL at /mysite/sql_searchMyDB>
     * Module Products.ZPsycopgDA.db, line 206, in query

If I query the PostgreSQL DB without umlauts, I get the results from the 
ZSQL method but on Zope Server #2 the umlauts are not displayed properly 
in the ZMI. On Server #1 the umlauts are correct.

I don't know if there is something wrong with my Zope or Python 
installation or if there is any difference between "psycopg2-2.0.5.1". 
and "psycopg2-2.0.6".

Any ideas?

Any tips are much appreciated.


Regards
Nico