Microsoft Access Consultant

We need the expertise of someone with experience using Microsoft Access over the 'net. We created an app which connects to an Access databse on a remote computer. We specify the address os the server, the path and filename, and proceed as usual (using ADO connection, in Visual Basic). It works fine using XP. However, we've found that when the client machine is running Windows 7, the connection does not work. Also, we've found that it works on one server running Windows 2003 Server, but not on another machines running the same server software. We need your expertise to help us resolve this problem.