The error 651 message is common on Windows 7 through Windows 11 and usually appears in a small pop-up window. The actual text varies slightly depending on the cause of the connection problem, but always contains this text:

While error 651 is annoying, it is a relatively minor issue. It should not cause your computer to crash, reboot, or display the blue screen of death.

Error 651 indicates that an attempt to connect to the Internet has failed, or that an existing connection has been terminated. There are a number of issues that can trigger the warning, from incorrect placement of a SYS file, incorrect modem setup, corrupt registry files, an IP address conflict, and driver problems to problems with your Internet Service Provider.

Considering the number of problems that the Error 651 message can cause, there are many approaches that you can use to resolve the issue. Here are a few things to try.