try to start jboss as root
The default install doesn't use privileged ports, so root should be unnecessary. Is the JAVA_HOME evironment variable set, or is the java executable in your path?
Besides checking those things, make sure nothing else on the server uses the same ports as JBoss (8080, 8083, 8009, 1099, 4444 8090, 8091, 1476, etc. -- this is off the top of my head, check the documentation or another forum thread). Beyond these things, we really need to know what the error message is.