Strongly recommend not loading anything past 5.0a for now. once you can get that to work you can then load later versions.

also check in SYSTEM -> FACTORY -> BACKUP the original .mem file may be there. You might be able to copy that back to the root directory and reload (f10 and unplugged) once thats done try loading a later version

dont forget recent version must be loade in the correct order.

Also. double check you are loading the correct OS for Audya others will not load as the type is wrong.

EDIT: I just noticed something - you have an Audya 4. are you certain the OS is 4.2B? I thought they were all shipped with 5.0a from new.