Non Compatible with JRE 6

I am using SOAPUI PRO with eclipse IDE and I am facing the following error.

def node = holder.getDomNode("//ns1:"+TempTag[1])
node.setNodeValue("abc")

Caught: java.lang.LinkageError: loader constraint violation: loader (instance of <bootloader>) previously initiated loading for a different type with name "org/w3c/dom/NamedNodeMap"

Is it due to difference in NamedNodeMap.class file in xml-apis-2.9.1.jar & rt.jar in JRE???

Yes, when I removed the xml-apis-2.9.1.jar it solved the issue for NamedNodeMap.class but was followed by TypeInfo.class error.

Could you please revert with a solution asap,

Thanks,
Karthick M