NuSoap returns extra characters

I am using NoSoap to host web services and it's been good since this weird problem happened. For the xml output it will produce extra 3 charaters prior to soap xml, wchich caused xml parsing error. I used Fiddler to capture the output. Anyone knows about why di this happen? Thanks in advance

HTTP/1.1 200 OK
Date: Mon, 18 Apr 2011 06:00:45 GMT
Server: Apache/2.0.54 (Fedora)
X-Powered-By: PHP/4.4.0
X-SOAP-Server: NuSOAP/0.7.3 (1.114)
Content-Length: 36993
Connection: close
Content-Type: text/xml; charset=UTF-8

???<?xml version="1.0" encoding="UTF-8"?><soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w... ... ...

Make sure there is no BOM (which is 3 bytes long, when using UTF-8) at the beginning of any of your PHP files.