To get JBoss 5.1.0.GA working under Oracle's JDK 1.7, you might run into this error when starting JBoss:

Error installing to Instantiated: name=AttachmentStore state=Described

The solution is to edit the file

conf/bootstrap/profile.xml

in your JBoss installation by locating the definition of AttachmentStore and changing it to start with:

<constructor><parameter class="java.io.File">