I'm using Corel PhotoPaint 10. A friend of mine is using Corel PhotoPaint 14 and is having the same problem...
When we create high resolution JPG files with PhotoPaint, they can not be seen with Internet Explorer. I've tried with ver 6, 7 and 8, all at default settings.
The files show up as little boxes with red X in them regardless of the dimensions of the file. I know it's there, because, if I right-click the file and say "save target as", I can save it to my desktop, double click it and see it. If I open the file with Microsoft picture publisher or Paint, modify a pixel and save it, it is fully visible on the web page. The resultant image quality is lost, of course.
What is my (and my friend's) PhotoPaint doing to the files that is making them incompatible?