A damaged connection file may be causing the problem. I know how to do it with aol which is as follows:

Go into the control panel and ensure you are in classic view. Go into add/remove and look for the isp connectivity service. If there click repair and restart the computer. Sign on to the isp again and the modem will be detected. Confirm the modem type and click next and next again. Choose the access numbers and click next and you will be returned to the sign on screen.

As I have said this is how to do the repair when using aol and I don't know if it is the same for other isp software. Maybe one of the experts on Vdr could help.

The only other I could think of would be to totally uninstall the isp software and the modem and reinstall.

Sorry if this doesn't take you anywhere.