When I create an EJB Project (either by the EJB Project wizard or the EAR wizard) the server is configured to deploy it as "project-namenull" instead of "project-name.jar".
I can fix this by opening the server (double-click on server in the server tab), going to the Deployment tab and editing the "Deployment Location" to correct it.
This doesn't appear to happen with any other deployment type.