Cannot publish an EAR to JBoss 6.1 server on JBDS 7,

Issue

When publish/clean, this message shows up and publishing can't be completed.

Could not publish to the server.
org.eclipse.jst.j2ee.application.internal.impl.ApplicationImpl cannot be cast to org.eclipse.jst.javaee.application.Application

Steps to reproduce:

1. Create a simple JEE6 EAR project, and add application.xml to META-INF
2. Add lib folder to project containing a jar.
3. Right-click project and select Properties, then Deployment Assembly
4. Add the lib folder to the list.
5. Select OK and receive this message:

An internal error occurred during: "Updating status for JBoss EAP 6.1.0 Runtime Server...".
org.eclipse.jst.j2ee.application.internal.impl.ApplicationImpl cannot be cast to org.eclipse.jst.javaee.application.Application