[rules-users] [Newbie] XML Package Reader: how to avoid this exception?

Hi everybody. I'm a happy user of the Drools 3.0.5 XML package reader, it seems working fine, but when I try to include an extra library (not Drools-related) in my build path, comes up this exception: Exception in thread "main" java.lang.RuntimeException: AElfred parser is non-validating at org.drools.xml.XmlPackageReader.read(Unknown Source) at org.drools.xml.XmlPackageReader.read(Unknown Source) at org.drools.compiler.PackageBuilder.addPackageFromXml(Unknown Source) at com.sample.PackageWriter.main(PackageWriter.java:39) It won't occur if I remove this "extra" library from build path (which uses a XML parser as well). Maybe I need to specify which parser Drools needs to load, but I don't know how. Sorry, I don't have enought java/xml experience to solve this. Could someone help me? Thanks in advance. FG