DOORS <--> RTC integration : Peer not authenticated

We're integrating RTC 3.0.1 with DOORS 9.4.0.4 on a Windows server.
When trying to add Friend from RTC, we get following "An error occured while requesting the root services document from server....."
....Peer not authenticated....CRJAZ1575E

We're able to browse Project Areas from DOORS, but gets a permission error when trying to create a task (which is probably triggered by the missing friendship above).

Can anyone tell me, where I can find more info about the rootservices document ?

Thanks.