warning leading white space!

Warning message from google

Leading whitespace
We have detected that your Sitemap file begins with whitespace. We have accepted the file, but you may want to remove the whitespace so that the file adheres to the XML standard

i used http://www.sitemapdoc.com/

all seemed ok last month, whats wrong? what do i do?

all help much appreciated.

 

leading whitespace means you have

newline
space
tab

or something like that in front of the first <