Why am I seeing "Could not parse url [resource:jboss-log4j.xml]" in my JBoss EAP 5.1?

Issue

When running my JBoss EAP instance, my server is not working and the server.log is occupying 500MB with many error messages. One of these messages is that below:

6:21:24,984 INFO  [JMXKernel] Legacy JMX core initialized
log4j:WARN Fatal parsing error 376 and column 18
log4j:WARN The string "--" is not permitted within comments.
log4j:ERROR Could not parse url [resource:jboss-log4j.xml].
org.xml.sax.SAXParseException: The string "--" is not permitted within comments.
at org.apache.xerces.parsers.DOMParser.parse(Unknown Source)
at org.apache.xerces.jaxp.DocumentBuilderImpl.parse(Unknown Source)
at javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:180)
at org.apache.log4j.xml.DOMConfigurator$2.parse(DOMConfigurator.java:612)