There seems to be a regression in maven-3-beta-3 related to the assembly plugin. When building a multi-module project using Maven 3-beta-3 I get the error "Unable to obtain archiver for extension 'zip'". This error does not happen with Maven 3-beta-2.
I wasn't able to reproduce this problem with a smaller project. The source can be checked out from the jboss repo
The problem can be seen running building certain modules.
I will try to narrow down the problem further if I have some time.