Sorry, as Dazz pointed out we lawyers like to enrich ourselves first, which means taking a long time to say something since we charge in 6 minute blocks :)
In other words if all the plaintiff can come up with is an unjust enrichment argument then they pretty much have nothing to stand on and their case is weak.
Ahem....boomtown is talking about your 'cause of action' - i.e. where you get the right to sue. Unjust enrichment is rooted in equity, not in common law. Although some argue it is just something made up and has no place in either.