Cells no longer highlight when selected
 

In Excel 2003, a weird problem just started occurring where if you select
multiple ranges of cells (i.e. using Ctrl-Select), the cells being selected
are no longer highlighted (although the rows and columns of the selection
are). This just started happening, and I don't know why or how to fix it. The
cells are still being selected, but it's much more difficult to see because
the bold border isn't shown around them.