Viewport Issue

Hi there, I dont know what I did wrong but I must have changed some setting. In any of my viewports, the object can be seen perfectly (Smooth + Highlights) but when I pan the viewport the object disappears and there is like an outline (like guidelines) of the 'box' which surrounds the object, then as soon as I stop panning the object reappears and the guidlines disappear. I reckon its got something to do with a setting on rendering the object while panning the viewport?

Hi Matt, you are reffering to smooth+highlights? Does this mean you're using gmax? Or pherhaps an older version of 3ds max?