I set up ACS 4.1 on a Windows2003R2 Member Server with Servicepack2. I did all the configuration and it looks like the ACS server can see AD (I can see all AD groups in Groups managemant of ACS). However, if I try to authenticate a user against Windows database, I get always a failed attempt with "Internal Error" in the log.
Looking at the log file in CSAuth, I can see the following lines:
pvAuthenticateUser: authenticate '***' against Windows Database
External DB [NTAuthenDLL.dll]: Starting authentication for user [***]
External DB [NTAuthenDLL.dll]: Attempting Windows authentication for user ***
External DB [NTAuthenDLL.dll]: Windows authentication FAILED (error 6L)
Unfortunately, I can't find anything about this error. Any idea?