When using the scroll wheel on my mouse to zoom in or out on a drawing, the symbols disapear, leaving just the grid. If I click the zoom to drawing button, the symbols reappear. I have to use the zoom buttons, or zoom window to perform any zoom functions. Any ideas?

Here is a file that exibits the problem. It is a problem with any file i use on this machine however. It seems to be machine specific, but I can't put my finger on what would cause it.

Thanks