Marc - Call Barbara Shoemaker in their accounting dept at (412) 650-1712.  She is a sweetheart and will get you paid immediately.  I guarantee you, the invoices just have never gotten to her desk.  Perhaps the company can come up with a better system of where the invoices are placed when received - I don't know the answer.  That is an issue that they have to figure out for the benefit of their own company.  She is very much on the ball and actually so is her assistant.  She will probably have you fax the past due invoices directly to her and will give you a number.