see this thread for details on troubleshooting the headers already sent error:
showthread.php?t=19285
on this page, i think the issue is the last one discussed in that post:
2) The Unicode Signature (BOM) PHP bug. the forth screen shot shows the Title / Encoding category of the Page Properties screen (Modify - > Page Properties). Checking the Include Signature (BOM) option can cause the headers already sent error 


