DC console has schized out!! It's trying to load a previous backup

I got a backup of MDK2, I use a utopia boot disc, MDK2 loaded, started to play then very nasty sounds from drive.
Switched off, removed disc and played another but was o.k.
A day or two later after playing other discs, original and backup console starts to display 'Cant find disc MDK2' regardless of what disc is put in.
It powers up o.k. but when starts to read disc gives above error.
Anybody else experience this, looks like most expensive back-up i've ever made.