Terminal service clients

We have been having an issue with our terminal servers. It seems that all the clients connected lose their internet connection. Resetting the subnet to 255 and then changing it back to 240 temporarily fixes the problem, the downside to this is that it cuts there connections to our unix server where they are actually doing most of their file modifications and it is also a pain in the you know what to keep doing this 3 or 4 times a day. any suggestions or ideas would be very appreciated. Thanks