If you unplug the Universal Serial Bus (USB) cable for an Integrated Services Digital Network (ISDN) modem that you use for both incoming and outgoing traffic while the modem is dialing, you may receive the following error message:
Error 651: The modem (or other connecting device) has reported an error.
After you plug the modem's USB cable back in, you will receive the error each time the modem dials until you restart your computer.
This error may also occur with other hot swap technologies, such as Personal Computer Memory Card International Association (PCMCIA), but this behavior has not been confirmed by Microsoft.
This error occurs because of the way Windows remote access handles both incoming and outgoing lines for the same USB Plug and Play device.
To resolve this problem, obtain the latest service pack for Microsoft Windows XP. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
322389 How to obtain the latest Windows XP service pack
To prevent this error from occurring, do not unplug the USB cable for the modem while the modem is dialing.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Microsoft Windows XP Service Pack 2.