Sounds like something on the ISP end.
A lot of ISP's will disconnect you if you are idle for 10-20 minutes. This is nothing new. The trick is to either have a router that keeps it 'live' or keep up something like outlook, gmail, or something checking e-mail every few minutes.
I've heard some routers do this as well, sending small packets to keep the connection live, but I do not have any direct experience.
If you have something (like e-mail) active, then it will show on the ISP end that you are still active, and not disconnect you.
