problem with default installation of forefront client security

hello,

we have the secound time an installation problem with forefront client
securtity (fcs).

fcs is installed on one server (sorry all in german, so i hope i
translate it correctly) with the defaults.
if you start the MOM 2005 management console, go to management, global
settings and then on security, the Mutual Authentication is "on"

on the client site, where we install the agents also per default, the
Mutual Authentication is standing "off"

the server an the clients are members of an 2003 active directory

so the first question is: why are they both so different ?

if i change on client site the Mutual Authentication to "on", and
restart the client, a get the following eventlog view:

Event Type: Error
Event Source: Microsoft Operations Manager
Event Category: None
Event ID: 26023
Date: 9/9/2009
Time: 6:40:42 PM
User: NT AUTHORITY\SYSTEM
Computer: DC1
Description:
The agent is configured to require Mutual Authentication, but the
MOM Server
host/Forefront is not in a trusted domain. Until the agent
and/or server is reconfigured the agent will not be able to talk to
the MOM
Server. To reconfigure the MOM Agent, re-run setup and disable mutual
authentication. To reconfigure the MOM Server, disable mutual
authentication, commit configuration changes, and restart all MOM
Servers in
the management group


on the MOM server we have also make a commit.

i know that if i make the Mutual Authentication off on both sites, it
will function, but i want use the Mutual Authentication !!

any idea's ?????

kind regards

Holger