I think your relative path is causing problems for JBoss. Specifically, it does not seem to be able to be able to create the temporary directory structures properly. To test this, try giving an absolute path and see if the problem goes away.
Nope, that's not it. That is an absolute path. In fact, when I change it to "file:/eclipse/etc" it does the same thing. And just before the error, it days
"[EmbeddedCatalinaService41] deploy, ctxPath=/Backoffice, warUrl=file:/eclipse/workspace/NextGen/Backoffice.war/