Misleading Article?
Yes, the update blocks access to files in some formats but not Office 2003 native formats. By default it blocks some foreign file formats and some OLD formats, PRE Office 97. Many commenters seem to have got the wrong end of the stick probably because the article could be read as saying Office 2003 could no longer open its own files.
The blocking can be turned off or down either by editing the registry or by group policy and searching for the error message will lead you to instructions on how to do this. Perhaps it is a bit draconian but warning that a file "may be unsafe" and then allowing you to open it anyway might be thought a bit lax by some people. A case of "damned if you do and damned if you don't". Not everyone is an expert and Microsoft has to cater for those people too. It chose the "safety first" approach.
Simon Jones
Contributing Editor
PC Pro Magazine