There is a flaw on the third service pack for the Office 2003 software suite according to Microsoft. The problem is that it cannot open some files.

“By default, these file formats are blocked because they are less secure. They may pose a risk to you.” These files include Word 2003, PowerPoint 2003, and Excel 2003 formats.

They have a solution on how to getaround this problem since the default action does not permit on opening some of those files.

Source: The Register