Domain User can be added to BPC by administrator but cannot access BPC

Dear experts,

we have set up BPC 7.5 NW SP09 with users from active directory. It is possible in BPC Administration to access the active directory domain and add the relevant user. When this user then tries to log on to BPC he gets the error message 'The user ID, password or Domain cannot be authenticated.' He can access with his normal ID and password after we added him also as administrator in the local windows server where BPC-Web component is installed on.

We already went through SAP Notes 1422163 and 1381073.

Does anyone of you have a good idea? How is the communication of BPC and active directory set up? Do the systemusers (BPC_ADMIN, _SYSADMIN, _USER) have to be part of the active directory?

Thanks and best regards

Felix