we are having ACS server primary and secondary running 4.1, there is authentication problem when trying to authenticate from primary, if we switch off the primary acs, authentication from secondary works fine. We restarted the system and services but the result is same.
Note: Local Users are getting authenticated from primary but when authenticating AD users then only we see the internal error.
checked the logs in acs which only shows the internal error.
need expert suggestion to troubleshoot it.
I have this problem too.