A very dumb problem that was getting to me yesterday. Highlighting on selected objects didn't show up in the perspective view (though it worked on front / side / top etc.)
I knew that I must have accidentally checked / unchecked a box somewhere but couldn't find it. I'm even sure that I tried the "show" menu in the persp view but I can't have been looking very carefully because it turns out that - when I looked again this morning - there it was!
So, to solve the problem: in whichever view you're having problems with go to the "show" menu and make sure that "selection highlighting" is checked. (In my case I had to uncheck and re-check it to get it to work.)
Hope that helps anyone else who's temporarily lost in maya menus :)
