Can’t See the Options On the Excel 2007 QAT “Line Style” Command

[SidBord]

On my Excel 2007 QAT I have the icon for what is called the ”Line Style” command. I use this command with the “Line Color” command a LOT. When I click on the “Line Style” icon I usually see a dropdown list of all the options for creating a cell edge line.
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Suddenly today the only option I see on the ”Line Style” dropdown list is “No Border”. All the sample lines that should be displayed are gone. Fortunately, this malady seems to be occurring on only one worksheet of only one workbook.
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I tried changing the line color with the “Line Color” command, and IT WORKED! Also if I select any of the "invisible" line styles in the “Line Style” command, they seem to work OK. I just can’t see any of the examples displayed.
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This suggests that the sample line styles (maybe) are all colored white, so they can’t be seen on the dropdown example list. But how in the world did the font color for the Line Style command get changed to white (assuming it is)? I wouldn’t think that there is an option to change the font color of a drop down option list. Or is there??
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Anyone understand this?
Sid