Echange 2000 on a domain controller and OWA

I have a problem with OWA
We have 1 domain and 2 sites
On each site we have an exchange 2000 server
On 1 site the exchange server is a domain controller
On the other site the exchange server is a member server

Connecting with OWA to the the member-exchange is no problem.
connecting with OWA to the dom.contr-exchange is not working.

Has anybody the same problem and found a solution ?
Can you log/debug something ?