Terminal Services dropping connections?

I have an interesting situation here. We have a remote office that connects to a server running a real estate closing called SoftPro via Terminal Service Web Access over a VPN. What happens is the users get “dropped” from from the connection and they end up back at the TS login screen. They reconnect and end up exactly where they had left off before getting “droped”. I am assuming this is an issue with TS not the application since the app appears to continue to run. The timing of the drop is inconsistent, sometime 5 minutes sometimes 25 minutes or it will work all day. My first guess was the connection was timing out, but am not sure. Any ideas out there?