Dehilight doesn't work for a net

Hi,

I've assigned a color to one of my nets in Allegro 16.6. When I want to dehiligh it, it doesn't work!. I see below message in the command section but nothign changes:

Net "Ag" dehighlighted. 

I've done many things: running DB Doctor, trying to hilight it first and then dehilight it! (last case doesn't also work). That net only keeps the color I had assigned to it and nothing can be applied on it!. niether Highligh nor Dehiligh. 

I would appreciate any help.

H.M