I didn't have this problem until I did what you said and I too, re-created the same problem. what I noticed is this. Applying a vray material and checking show in viewport works fine as long as my viewport is set to [shaded + edged faces]. However, if I go to the viewport menu and select - materials > shaded materials with maps - I also lose the bitmap in the viewport. BUT I noticed that the reason this happens is because the second you click on "shaded materials with maps" the "show in viewport" button resets itself to be turned off. clicking it back on returns the bitmap to the viewport.
so while you check the material to show in viewport, using the viewport menu to select shaded with maps cancels it out. I'm guessing because this is the same command in a Global sense? the viewport menu option turns ALL maps on and off as a toggle. where as the "show is viewport" is a per material command.