Hello,
3. It happens with a wide variety of fonts.
4. When opened with one of Adobe's pdf readers (Adobe Reader, Acrobat Pro), the file always looks fine.
That's extremely odd. Can you send a sample PDF file (along with the source code) for us to inspect it? I'm using Mac OS 10.5 on Intel, so I'd like to confirm the behaviour you report.
5. Opening and closing the file can make the problem parts change. So, for instance, opening and closing the file can make it so that roman letters show while italic letters are crossed boxes or vice versa. Usually, if I do this enough, I can get to a normal view with all letters looking like letters.
That really doesn't make sense at all. Sounds like a problem with the Apple code analyzing the PDF file, but I've never observed such a bizarre behaviour myself, and I use mostly Preview on the Mac to view PDFs. Arthur