What else is going on? Do you have a viable product? Is it not selling? Or is the problem that he says that it's selling but there's no paycheck anyway? Does the product's market make sense to you? How does your product stack up against the competition? In other words: is there any point to sticking around, even ignoring the paycheck issue?
If you have doubts about the company's prospects, and they are being cagey about how things are going, I'd probably leave.
If you think the company has a bright future, then I'd dig deeper into the paycheck issue, maybe asking the founder why he's being so secretive. Have with him the conversation you're starting here. (Him thinking you are about to leave might not be such a bad idea. Hard to imagine that would be a surprise.)