I will need to have a copy of the page in question. If you can please post back and include this in a zip archive so I can take a look at it and try to find the problem.
This error about the headers already being sent is one of the most common that you will encounter in a php page. It is almost always due to some sort of white space that occurs outside of the php blocks on the page, most of the time it is the first character in the file.