[leif]

Most people know what's fair, somewhere deep down. You know it, and they know it.

Go to them confidently, tell them "You didn't pay me. I know your company's having problems, but that doesn't get you out of your debt to me, we both know this. How can we make this right without destroying our friendship and the company?"

If they don't give you anything to work with (you should accept either money or a solid explanation of why they can't pay you now, and a concrete, explainable timeline showing exactly when they'll be able to), then either they're clearly disrespecting you and their social contract, or they actually are completely bankrupt and have no hope of getting out of it, and in either case, it's perfectly within reason to start them down the bankruptcy path.