XML comparison failing on namespace URI not being mapped to any prefix

Hi all,
I have a little XML comparison tool called 'diffx'. I run it from the command line and when I give it 2 XML files it throws an exception stating:-
"namespace URI . . . has not been mapped to any prefix"
Can any one please take a look at the tool and see how I can get it to avoid this
Below is the two lines of XML it is comparing and the entire error message.
Many thanks in advance!!!

Error Message:-
                                            <executionDateTime><ins>2010-04-19T04:15:55Z</ins><del>201
0-03-24T16:51:46Z</del></executionDateTime>
                                com.topologi.diffx.xml.UndeclaredNamespaceException: The n
amespace URI "http://www.xxxx.org/2007/FpML-4" has not been mapped to any prefix.
        at com.topologi.diffx.xml.NSAwareXMLWriter.getQName(NSAwareXMLWriter.java:599)
        at com.topologi.diffx.xml.NSAwareXMLWriter.openElement(NSAwareXMLWriter.java:373)
        at com.topologi.diffx.event.impl.OpenElementEventNSImpl.toXML(OpenElementEventNSIm
pl.java:214)
        at com.topologi.diffx.format.SmartXMLFormatter.format(SmartXMLFormatter.java:203)
        at com.topologi.diffx.algorithm.DiffXFitopsy.process(DiffXFitopsy.java:304)
        at com.topologi.diffx.Main.diff(Main.java:314)
        at com.topologi.diffx.Main.diff(Main.java:289)
        at com.topologi.diffx.Main.main(Main.java:332)

XML lines that it is comparing:-
<trade xmlns="http://www.xxxx.org/2007/FpML-4">    (its the same in both XMl files)