um, i have never seen this...
I have no idea. What does your deployment look like? Can you jar into into an example I can run? And, can you log an EJB3 jira task?
May just want to grab a clean install of JBoss 4.0.4RC1 (remember to install with EJB3 support) and follow the Seam demo here:
I've seen some pretty screwed up ZipExceptions when the archives were either missing or corrupted. The TestNG tasks work for me under this setup.