OpenSAML user discussion

I have code which builds a SAMLResponse.  The code works fine b/c I unit 
tested it using a j-unit test case through eclipse and I can see the correct 
output of the SAML response via toString in the SAMLResponse object.  When i 
call the same toString method running within a Tomcat web application, I get 
the following exception:

389094 [http-8080-Processor23] ERROR opensaml.SAMLResponse toString - caught 
a SAML exception while serializing XML

I am running 1.4.2_04, tomcat 5.x.  I overrode the xerces, and xml-api jars 
in tomcat with the dom3 capable jars included with the openSAML build in the 
TOMCAT_HOME\common\endorsed directory.

I'm assuming this is a configuration issue.  Has anyone run into this or does 
anyone have any suggestions as to where to start?

Thanks,

Jason P.