I read about this with great interest this morning. Seemingly, PhotoShop 7 embeds some xml code in jpeg images when saving them using the default "Save As" menu, and not the "Save for Web" feature. This XML code breaks some builds of IE6 for Windows.
I've read that JFIF (JPEG File Interchange Format) has supported additional text for quite some time, and this use of it to include XML in general (and RDF/XML in specific) is nothing new, and not limited to Adobe (who have been doing this since 2001).
It would be interesting to see where the problem lies with this, but I have yet to read an explaination for it.