I have a problem I've never seen before. I have created several drawings for use as xrefs. When I bind one in particular to any drawing, it disappears from the drawing yet is present in the layers albeit commuted to just three layers (the other layers of the xref are there but as empty layers), and it is still shown as an xref in the manager.
 
Any ideas?
(we are using Acad 2009)

When you bind an xref it turns it into a block in the file.  It might be on a layer that is turned off or frozen, or maybe some of the other layers that it is using are off.  Turn everything on and see what happens.

I have managed to overcome the problem caused by proxys. If you switch the layers off and lock them, then wblock the dwg, you leave all the proxys behind in the old version and then the dwg used as an xref will bind ok.
 
 

great!  I'm glad you got it to work.