I'm having the same issue and so far no solution. Fortunately, it is not affecting the performance. To review the log info I'm using the ConsoleAppender and then redirecting the output to a file but I'd like to find a way to fix this error.
Did you manage to resolve your problem?
Is it possible that JBOSS is trying to get an instance of org.jboss.logging.appender.FileAppender but a different jog4j is overwriting the settings?
the log4j.properties is in the run.jar file. try updating the log4j.appender.FILE to this.
since lib/log4j-boot.jar is in the runtime, it should use that instead of the jboss FileAppender.