When they (people in NV) are using your application are you setting the application to use the Frame-Relay or the Internet to communicate with the AS/400?

I know they are both running TCP/IP but maybe if you use the Internet Address of the AS/400 instead of going through the router it won't time out.

You can also set up ODBC not to time-out so soon. Play with the ODBC settings and increase the time it should wait before timing out.