It's not that it doesn't open ANY files from previous versions. It's that some
earlier versions stored shapes in a way that made it appear to PPT 2003 like a
an attempted buffer overrun exploit (ie, a worm), so PPT would refuse to open
the file rather than risking exposing your computer to who-knows-what evil.
If the problem had arisen during testing, it would have been fixed prior to
release, no doubt (especially considering how quickly the patch for the problem
was made available once the problem came to light).
Given the wide variety of hardware, software and PowerPoint file versions this
thing has to support, it's no wonder that problems sneak through. It's just
impossible to test all the combinations.
Point taken .... I guess I am guilty of believing the worst about the developers :-( <slapped wrists for me!!>