I changed my Receive buffer to 1 notch lower and it started working fine again. This change had been made when I purchased a new computer.
You go to Dial Up Network, right click the phone connection you use to log on with, choose to "configure" jsut under the modem info, hit the "connection" tab, hit " advanced" tab, and then slide the "receive buffer" down one notch.
See if it works for you, otherwise you will need to do a ping routine like Pyro is suggesting and he can then tell you what's going on with the hops and connects.
Hope it helps.
Ranger Bob