Office 2003 Standard (Enterprise), Windows XP Pro

A user in my office is having a bizarre issue in Excel only: the worksheet
is "whiting out" except in a small square. The content is not lost - if you
flip to another application, then reactivate the window, it reappears for
about 3 seconds, then disappears again. All formatting and contents are
invisible...even the gridlines are gone. Only the object layer stays put.

This occurs in multiple files on his computer only. Anyone else can open
and use them without issue. The Detect and Repair utility had no effect.
The Help Desk has been less than helpful.

What setting could he have changed to cause this?!? Any ideas?

Thank you!

Erin