If the router runs into a problem of 100% CPU affecting the internet connection, normal courses of actions include re-booting the router, power recycle the router and applying the latest firmware.

If none of the above works, check the computers that have a wired connection to the router. The problem may be caused by one of those computers that require a restart after Windows update. If that is the case, simply restart the computer to finish the update process and the router problem should go away.