Hmm, I haven't seen that before.
Do you have the jboss repositories defined in your settings.xml?
Are you specifying the 2.1-jboss-1 version of the jar plugin in your pom?
I will try to reproduce the problem locally.
It seems to be a bug in the maven plugin resolution. It looks like it's getting the pom for maven-jar-plugin from the central repo, and then getting the jar from our repo, and then getting confused about which one it has.
If you explicitly set the version in your pom it seems to resolve the issue. Just add
to the plugin declaration in the pom, and the problem goes away. It also works fine if you set the version to 2.1-jboss-1, so I don't think it's a problem with the patched plugin by itself. Just a problem when you don't set the version and maven doesn't seem to be able to figure out which one to use.
I created this issue to remind myself to try to fix this when I have time.