I'm not so sure it was the background now. OK I've narrowed it down. I removed the custom background, and it still won't open. So I went page by page and it turns out to be a font issue. Apparently I had one page that used Arial Narrow. Once I changed the font to something both PCs had the file opened fine. This is odd behavior, you'd hope for better error messages than that. One would expect the font to default to something else kind of like on a web page. I have a relatively small file, so I couldn't imagine trying to find the proverbial needle in a huge file haystack. I was just lucky I guess.