first question: did you deploy an app which contains JAXB jars?
second question: do you use the JBossTools plugin, or "plain" Eclipse with WebToolsPlatform plugin? The latter some trouble with recent JBoss servers, because the JBoss endorsed dirs are not configured properly. See https://bugs.eclipse.org/bugs/show_bug.cgi?id=250643 - the last comment has a link to the JBoss forum, and there you will find a way to configure the server properly.
Hope this helps