The Ingroup function was working fine on 9X clients but does not work any longer ( still works on NT clients ). Not sure if someone rolled a hotfix or something and did not tell us and if that what broke this. We have a 95 machine that was offline for over a month and seems to work fine. We took the NETAPI.DLL from that machine and tried it on a failing one but it did not help.
We are using the RPC service and nothing has changed in it's configuration.

This is the error log:

2000/05/30 21:02:07 - Error occured during retrieval of local network information Error : The system cannot find the file specified. (0x2/2)
2000/05/30 21:02:09 - Error occured during retrieval of remote network information Error : The system cannot find the file specified. (0x2/2)
2000/05/30 21:02:09 - Failed to locate/connect to a KXRPC server Error : The network path was not found. (0x35/53)
2000/05/30 21:11:57 - Failed to locate/connect to a KXRPC server Error : The network path was not found. (0x35/53)
2000/05/30 21:14:46 - Error occured during retrieval of local network information Error : The system cannot find the file specified. (0x2/2)
2000/05/30 21:14:47 - Error occured during retrieval of remote network information Error : The system cannot find the file specified. (0x2/2)
2000/05/30 21:14:48 - Failed to locate/connect to a KXRPC server Error : The network path was not found. (0x35/53)
2000/05/30 21:22:56 - Failed to locate/connect to a KXRPC server Error : The network path was not found. (0x35/53)
2000/05/30 21:33:41 - Error occured during retrieval of local network information Error : The system cannot find the file specified. (0x2/2)
2000/05/30 21:33:43 - Error occured during retrieval of remote network information Error : The system cannot find the file specified. (0x2/2)
2000/05/30 21:33:43 - Failed to locate/connect to a KXRPC server Error : The network path was not found. (0x35/53)