Sounds rather ominous - and it can be. Big red warnings are scary! In this case, Mr Microsoft and Mr Asus have banged heads causing many machines to stop dead in their tracks.
Microsoft have recently changed an update (KB3133977 - which changes important boot files) so it is downloaded and installed for everyone. Some Asus motherboards are detecting these changes, and locking down systems!
If you're having problems with Secure boot violations, or a computer that won't start, contact us firstname.lastname@example.org and we can assist you in getting back on top of things.