Cannot Locate Objects on layer

This ones a bit wierd.

I've got a *dwg open, gone through all the blocks etc.

But i'm unable to delete some layers that are surplus to requirements.

Keep getting the dialoge box shown below

There are no xrefs in the drawing, no objects on the layer even in

blocks, and it is not the current layer.

Any Advice appreciated.

Ignore above post.

It was a block but one that was on another layer turned off so i couldn't see it