When you start to see the people as the problem, instead of the people in the problem, it can hinder your social problem solving. And this is as much a social problem as it is a financial one.
There is a chance that this can be resolved with (1) you getting your money back and (2) you still being on friendly terms, but probably not if you label them "assholes" in your head. :)
Generally speaking I don't advocate labeling people. My remark was included because many people in the OP's situation would feel terrible about asking money to a company that is struggling. However, it's important to remember that they are the ones at fault so a request is absolutely legitimate and he shouldn't feel bad about it.
I think you hit the nail there in that I'm really curious on how to solve the social problem in more of a win-win way as you described. I would probably break down and rank the problem like this:
1. Character - how do I carry myself with justice, mercy, and compassion, yet not get pushed around and maintain self-respect?
2. Social - how do I maintain relationships?
3. Financial - how do I get my money?
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.
It's tough. What helps me is to step back and look at the problem objectively. Think about the situation is if it were happening to strangers and you were a disinterested observer. How should the problem be resolved?
When I'm in a situation like this, it also helps to think of myself as an "ambassador of reality". Basically, reality is sending a message to the business people. It's feedback saying "your assumptions about the market were wrong" or "you didn't plan thoroughly enough" or whatever the situation is. Reality just happens to be sending this message through you to them. If you don't ask for your money back, you're not giving them the proper financial feedback that they need to learn to be better businesspeople. For their next venture, you will have helped them learn that if you don't pay people they won't just go away and forget about it. You don't have to be aggressive or threaten legal action, you just have to be persistent and not go away. :)
If you need some inspiration, go watch the film Gandhi. He was always civil and friendly, but very stubborn. :)
Okay, here's an interesting idea. First of all, make sure both of you agree that they owe you money and you agree on the amount. Get it in writing.
Then ask them to pay you a set amount every week to pay down the amount. No matter what their financial situation is, they certainly can pay you something every week. Insist on getting paid something, even if it's just $1! Collect the check in person every week. Email them a receipt with an updated balance due. It's a very visible reminder to them that they owe you money and it's a way that you will at least get some money back!
When you start to see the people as the problem, instead of the people in the problem, it can hinder your social problem solving. And this is as much a social problem as it is a financial one.
There is a chance that this can be resolved with (1) you getting your money back and (2) you still being on friendly terms, but probably not if you label them "assholes" in your head. :)