I'd guess that the % style in this workbook was changed by someone.
In xl2003 menus:
Format|Style
Select percent
Click modify and change what you want.
Styles live in workbooks. So you'll have to make the same adjustment to each
workbook that has the problem.
If you can find a workbook that has the correct formatting for the percent style
(maybe a brand new workbook???), you could merge styles.
Open the workbook with the good percent style.
Open the workbook with the bad percent style.
With the bad workbook active...
Format|style|merge
and choose to merge from the good workbook