Microsoft Office 2003 Service Pack 3 prevents access to certain file formats that the software assesses as being less secure, and bizarrely, it includes its own files.

SP3 will block access to some Excel 2003, PowerPoint 2003 and Word 2003 formats, as well as Corel Draw files.

Microsoft said: “By default, these file formats are blocked because they are less secure. They may pose a risk to you.”

Full details of the issue can be found in a Knowledge Base article on Microsoft’s website.

Note: A workaround has been provided for users who need to access such files but the default is to disable access.