Unpaid Sales Commissions
I am not an attorney, but have done hundred of hours of research. Here is what you need to look for in your sales compensation plan of record. WHEN WAS THE COMMISSION EARNED? (verse when it is payable). It doesn't really matter when the company actually pays you, but it's more important to establish "at what point in time" is the commission money earned.
Here is the downside from your situation... most companies have successfully proved that sales commissions are not earned until the customer has submitted payment. Many sales people confuse the point at which the company pays you commissions as the point in which it is earned.
If you are working a large strategic sale, be sure to see if you can offer the client a discount for payment upfront. Most sr. level executives will like getting the $$$ upfront, and you protect you sales commissions.
Last point, if you can prove your company somehow did not invoice the customer or deliver services in a timely fashion... i.e. the customer would have paid if your company would have responded in a timely fashion, you might have a small leg to stand on.