Subauthentication Package + Kerberos + Users migrate from Windows NT to 2k3

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Win2003

C++

Windows

Hello people,
I have a big problem: I have a DLL that implements subAuthentication LSA custom running in my network in Windows Server 2003 and this dll export only Msv1_0SubAuthenticationRoutine and Msv1_0SubAuthenticationFilter routines.
I also have many old user migrated from WindowsNT and I got a situation that these old users can not logon in domain if my dll is active, but new users can authenticate in domain if my dll is active.
I set up my custom dll in registry how say Microsoft site http://msdn.microsoft.com/en-us/library/aa379395(v=VS.85).aspx and Even I put a DLL with just the stub functions without any funcionalities (the DLL just resturn TRUE for the functions) the problem occurs.
Someone has experienced something similar? Got some clue to help me?

Thanks