Layer problems in drawings

  1. Layer Manager does not show in one drawing.  The drawing was created in DS by me.  Invoking the layer manager (either by icon or typing command) returns "error"  .... no other information and no layer manager.
  2. It used to be that UndoLayer was a very useful command for me.  It no longer works and returns the message "Restored previous layer status" but actually does nothing. It doesn't seem to matter what tool I used to change the layer status before: ie doesn't work if I used Layer Manager or Isolate layer, etc.

I tried upgrading from V1R5 to V1R5.2

The upgrade worked well in that I got the same user settings I had and the new version is installed (checked Help>About)

The same problems persist ...