For some reason all the pages I generate with PHP have 3 CRLF pairs (blank lines)at the start of the page. This doesn't seem to cause problems with normal HTML pages (except that you can see three blank lines in the page source) but my image pages no longer work because of this and I could'nt figure out where these CRLFs are coming from. I spent about a day working on this.
I found the problem and am posting this because I didn't find anything about this in a forum search and want to share this so others won't have to go through this.
The problem was cause by caused by having 3 blank lines at the end of a PHP include file after the final '?>' in the file. I'm not sure why PHP added these lines to the start of the output rather than in place where the file was included but others may encounter this problem.