AutoInvoice Error Message; A receipt method is required when a payment extension entity is passed.

 Hello,

The client is running the AutoInvoice Master Program 4 times a day, and on one of their Sales Orders, they've got the error message;

"A receipt method is required when a payment extension entity is passed."

They have only been LIVE since March 2, 2009, and this is the first time I've seen this error.  I have done some searches on MetaLink, but have not come up with a hit.  Does anyone have a suggestion on where I should look for how to resolve this error?

Thanks,

Kurt