NT to Online Server - password problem

I'm sure this has been discussed before, but I have the problem now, and I can't find it in the FAQ... I have a new Windows NT client (Informix/CLI 2.5) that I need to connect to Informix Online Server 7.12 on AIX 3.2.5. The Online Server configuration is definitely running. Other UNIX systems connect to it without difficulty. I'm trying to connect using ODBC, the driver that comes with CLI 2.5, from Microsoft Access 97. The NT system gets charming error -956, which means the password is wrong. I see messages in online.log on the server about the password being wrong. (This means at least the protocol, IP address, port number are right) What password? The UNIX servers don't use passwords for authentication, they take the userid supplied by the caller and check hosts.equiv / .rhosts. Any hints on how I make this work from ODBC? I think I need to have it send no password at all, but I've tried not supplying one and I still get -956. thanks, dwight