After having some trouble, I was able to solve it by killing all java applications, reinstalling jBoss' package, trying to start, stopping and starting again. Just doing some of these stepps, for some reason, was not working. It had to be all of them in that order. I don't know if there's a better way of doing it but, fortunately, that worked.
If someone knows a better way, just in case something similar happens in production, please do tell.