I'm trying to reset missing cell styles for a tab.

I have a spreadsheet that somehow has lost almost all of the built-in cell style formats.  All I can see is 20% Accent, no others. 

Copying the tab to a new spreadsheet removes most cell styles (except 20% Accent) on the newly copied tab.  All other spreadsheet tabs are also affected.  I've also tried copying and pasting the cells to a new workbook, and that creates the same style problem on all tabs of the new workbook that I paste the cells into.

I'm using Excel 2007, but I've also tried the spreadsheet on 2010, and have the same problem.

Any ideas would be appreciated!  Thanks.