The first thing I did was roll back using Restore to a couple of days before the event with no change and the driver rollback button is greyed out.
The keyboard works if I boot the computer into DOS.
I suspect you are right that it is a hardware fault.
I am just about to stick another blank HDD in and load a clean copy of the OS and see if the keyboard works then I think it will prove whether it is a hardware or software issue.