Trouble with RPC and Outlook 2003/Exchange 2003

Hello,

I have Trouble with a Computer who is in my Domain. The Domain is a
win2k only Domain, with DNS, Active Directory and all common things.
The Server is running Microsoft Small Business Server 2003. All worked
fine when i added the first computer to the domain, with adding a
Exchange 2003 Account to outlook 2003. But on the next computer i have
trouble, a messiges always appears: "The Systemcomponent RPC, whitch
is needed to connect with the e-mail server, isn't correctly
configured. You can get further information from the system
administrator." (something like that, translated from german). I can't
connect to the exchange server, always when i would like to add a
Exchange mailaccount this message appears.

What can i do? I belive its the client who makes this trouble... Can I
configure the RPC service?

Things that I allready did:
- Reboot :-)
- RPC-Services checked (all are running)
- Putted the computer in a workgroup and back into the domain.


Thanks for any help!

Regards
Stefan

(Sorry for this terrible english, but i hope its readable)