VPN on Vista acting WEIRD!!!

I am running Vista Home Premium. When I hook up to the VPN in the morning, all is fine until 1 pm local time, when the internet access starts getting spotty and the VPN disconnects, and I can't reconnect afterwards at all, even though the Internet is fine. My ISP says no problem from them, and the DSL provider says no problem there. I tried replacing the router (wireless) and as usual I get right in in the morning. I haven't to 1 pm yet with it, we'll see today, but I don't think it's the problem, rather something in Vista - but where????