Excel 2007 - Cell Styles - Normal no longer displayed

In one particular workbook, in the Cell Styles section, I can only see "Custom Styles" and I did not create the hundreds of custome styles now displayed. I've tried to delete many of these custom styles, but the other sections do not reappear.

I am missing the other sections normally available under Cell Styles such as "Good, Bad and Neutral" and "Data and Model" and "titles and Headings" others normally seen.

I need to modify the "Normal" as I have fallen victim to the bug where Normal has been set as the Long Date Format....

If anyone has any tips as to how I can get this workbook back to displaying all the routine Cell Style choices, I would be greatly appreciative.

I have attached a template of the workbook herein.

Thanks all in advance!