Windows 95 network timeout?

I have a Win95 pentium PC that was functioning correctly at one point in time. Windows was then relaoded for a different reason. It now routinely loses it’s network connection after 90 minutes of inactivity. I have replaced the 3COM card, reformatedand reloaded Win 95 two different times. I now have loaded only Win 95, the SP for it and the application that I need to run across the network and still recieve a timeout after 90 minutes. I have also loaded new drivers for the NIC. The hardware has not changed from when it did work. ANY IDEAS??

Thanks,