Contractor Dilemmas - Moral and Financial Obligations?

An Anonymous Coward asks: "This is a true story, one that I am currently trying to resolve and wondered if the Slashdot community could offer any help. I've been developing a new application for a startup company, contracted on a daily basis for my services. I've been providing services for 5 weeks now, and am still trying to get payment for work completed during week 1. The company is refusing to pay me, stating that they are not happy with progress, however all of the milestones we agreed upon for that week have been met. Now, it gets interesting: I know that this company is seeking startup venture capital, and I know from whom. Yes, it would be malicious to contact this party with the information that I have, but am I morally obliged to? If you were set to pump several million into a company with loose moral fibre would you not appreciate a warning?"