Error Message: Too few arguments

I'm getting an error message on the confirmation page on Marketpress. Everything seems to work, purchase goes through. It's when the user is redirected back to the confirmation page that I get:
Warning: springf() [function.sprintf]: Too few arguments in paypal-express.php on line 501

My first reaction is that it is a conflict with another plug in, but I'd like to get some opinions before I tear everything apart.
Anyone have any ideas?