OpenSAML user discussion

I was adding new JCE provider to the config.xml file in addition to many 
alrady specified in the config.xml located in xmlsec-1.0.5.jar. I got problem 
with ANY modification I made to config.xml, even addint comment line. I use 
the following shortcut procedure:
1) on win32 open xmlsec-1.0.5.jar with winzip
2) edit config.xml adding just single line:
<!--  This is the only modification to the file -->
3) save modified config.xml file back in zip.

When I run application that uses OpenSAML I got tons of errors during 
initialization, essentially:
    [junit] java.lang.IllegalArgumentException: InputStream cannot be null
    [junit]     at javax.xml.parsers.DocumentBuilder.parse(Unknown Source)
    [junit]     at org.apache.xml.security.Init.init(Init.java:142)
    [junit]     at org.opensaml.SAMLConfig.<init>(Unknown Source)
    ...

What is wrong with my shortcut procedure? What is the proper way to 
make changes to config.xml?

Thanks!
Konstantin