xml parsing error

I am downloading an xml file from my website (a php script that pulls data from a database) and using a XmlSerializer to convert the returned data to an array of my Card class.

Loading the file is working fine, however the XmlSerializer returns this error:

 InvalidOperationException: <cards xmlns=''> was not expected

I have looked through all of the php code and checked the returned xml document and nowhere does it add this xmlns='' to the root node, so where does it come from and how can I get rid of it?