If you try to redeply a webapp via jmx-console in JBoss/Jetty you may get the following error:

java.io.FileNotFoundException: C:javajboss-3.2.1...jbossweb-jetty.sar.webdefault.xml 
is alias of C:javajboss-3.2.1...jbossweb-jetty.sarwebdefault.xml
...

After digging into the sources I possibly found the bug in the toString() method of BadResource.java because the toString() method appends additional information to the original URL. The toString() method, however, is used by WebApplicationContext as the path to webdefault.xml.
I have already posted a mail on the jetty-discuss mailinglist. I will keep you informed about the status ...