At the moment jbossws throws a ClassCast Exception in case of an illegal webservice response (missing closing tag, etc...) :
[code]
Caused by: javax.xml.ws.WebServiceException: java.lang.ClassCastException: org.jboss.ws.core.soap.Te
xtImpl cannot be cast to org.jboss.ws.core.soap.SOAPElementI
mpl
at org.jboss.ws.core.jaxws.client.ClientImpl.handleRemoteException(ClientImpl.java:404)
at org.jboss.ws.core.jaxws.client.ClientImpl.invoke(ClientImpl.java:314)
at org.jboss.ws.core.jaxws.client.ClientProxy.invoke(ClientProxy.java:172)
at org.jboss.ws.core.jaxws.client.ClientProxy.invoke(ClientProxy.java:152)
at $Proxy311.bookOrders(Unknown Source)
at com.skidata.dta.server.co.v3_0.classic.impl.BookOrdersHelper.invoke(BookOrdersHelper.java
:46)
... 12 more
Caused by: java.lang.ClassCastException: org.jboss.ws.core.soap.TextImpl cannot be cast to org.jboss
.ws.core.soap.SOAPElementImpl
at org.jboss.ws.core.CommonSOAPBinding.getParameterFromMessage(CommonSOAPBinding.java:894)
at org.jboss.ws.core.CommonSOAPBinding.unbindResponseMessage(CommonSOAPBinding.java:634)
at org.jboss.ws.core.CommonClient.invoke(CommonClient.java:380)
at org.jboss.ws.core.jaxws.client.ClientImpl.invoke(ClientImpl.java:302)
... 16 more
[/code]

It would be helpful to get the actual Parse Excpetion from the xml parser instead of this classcastexcpetion.
Digging through the code i found out that this might occur because the MessageFectory to parse the response is initialized with ignoreParseErrors = true. e.g in the SOAPMessageUnMarshallerHTTP at line 82 (source .3.1.1.GA)
[code]
MimeHeaders mimeHeaders = getMimeHeaders(metadata);
soapMsg = getMessageFactory().createMessage(mimeHeaders, inputStream, true);
[/code]