File this under oops. An update to Malware Bytes security software marked some essential Windows system files as malware which would then cause the PC to be unable to boot. They have since disabled pulled the update from their servers. It seems on some computers the software flagged itself as bad! If you have been affected, you can try go over to their forums where a user has posted a guide on how to rescue your system if it can’t boot.
Note, except for this really big issue, Malware Bytes does work well on computers that are spyware infected.