This may be the source of the problem

Check this out................

http://support.microsoft.com/default.aspx?kbid=833258

The fill color, the fill pattern, or the line color of a WordArt or
AutoShape object in an Office document does not change

As directed, change the High Contrast setting in Windows OS


Gord Dibben MS Excel MVP

On Tue, 17 Mar 2009 17:02:01 -0700, Quandary
wrote:

In all excel files, I can not get either Cell format, or Conditional format
to change
cell colour. The dropdown Format window allows the formats whether it is
Cell
or Formula to be visible and when O K is pressed, Cell does not format and
no error info apparent. Border colours work, Cells are not Locked, neither is
the workbook. All this was working excellent up to a few months ago.
I would appreciate any help you can give me.