Problem running esql/c program

I have an application that accesses the database through a dll. The problem I am having is that I get an access violation when I start the application. It occurs during initialization so I am unable to set any breakpoints for debugging. The environment is Windows NT 3.51 using the Informix client 7.10 for NT. My compiler is Microsoft Visual C++ 2.2. The same source code works with Sybase and Microsoft SQL Server. A simple test program that uses the same database access dll would not work until I compiled it with 8 byte structure member alignment ( originally it was 1 byte ). It appears that there are compile and link options that I am not aware of ( maybe undocumented! ). If anyone has had any similar experiences or advise, it would be greatly appreciated! Thanks in advance.