I never had that problem. But before getting another US Robotics 5699B modem, after a T-storm, a US Robotics 5699B I had acted possessed, Windows all of a sudden would most of the time say "There was no dial tone" or similar and refuse to even dial, even when the telephone line was fine and after reinstalling Windows!! Then sometimes, it will dial and Windows says that it's connected, but all of the web browsers fail to find any web site, no matter what!! Obviously, that was because the modem got damaged by a spike. That was the only time that I ever had Windows refuse to dial with a US Robotics 5699B modem.