The stack of unpaid legal bills had become a problem as early as May. That’s when court documents show U.S. Capital Partners, a boutique investment bank, apologetically told Vedder Price it would propose a payment plan for invoices that the firm says grew to more than $800,000.

Yet the money never came, and so in August Vedder Price sued the client in New York federal court. Now the case spans two coasts, and the soured relationship has spiraled into a nearly $6 million dispute. Vedder Price, meanwhile, finds itself among a growing segment of Big Law firms turning to public court proceedings when traditional collections strategies have failed.