请告诉我为什么在Jboss AS7中部署时会出现以下错误。部署.ear时我抛出此错误，并且我使用了模块。但是，当我使用lib中的库部署ear时，它正在部署而没有任何错误。
Caused by: java.lang.IllegalAccessError: tried to access class org.apache.xerces.parsers.ObjectFactory from class org.apache.xerces.parsers.SAXParser
at org.apache.xerces.parsers.SAXParser.<init>(Unknown Source) [xercesImpl-2.8.1.jar:]
at org.apache.xerces.parsers.SAXParser.<init>(Unknown Source) [xercesImpl-2.8.1.jar:]
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) [rt.jar:1.6.0_38]
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) [rt.jar:1.6.0_38]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) [rt.jar:1.6.0_38]
at java.lang.reflect.Constructor.newInstance(Constructor.java:513) [rt.jar:1.6.0_38]
at java.lang.Class.newInstance0(Class.java:355) [rt.jar:1.6.0_38]
at java.lang.Class.newInstance(Class.java:308) [rt.jar:1.6.0_38]
at org.xml.sax.helpers.NewInstance.newInstance(NewInstance.java:51) [rt.jar:1.6.0_38]
at org.xml.sax.helpers.XMLReaderFactory.loadClass(XMLReaderFactory.java:187) [rt.jar:1.6.0_38]
at org.xml.sax.helpers.XMLReaderFactory.createXMLReader(XMLReaderFactory.java:180) [rt.jar:1.6.0_38]