Problem:

The delete button has stopped working on my keyboard in C3D? Have I turned it off somewhere by accident.

Also and an object on a layer, when selected won't update on the layers Ribbon it just shows the current layer.

I can't select more than one object at a time.

I can't select an object until I start a command

Solution:

These are symptoms on the noun/verb control in AutoCAD being changed.

Type PICKFIRST at the command line and change the value from zero to 1.

This should restore your usual AutoCAD behaviour.

This is a tick box in the Options form - Noun/Verb Selection.