Error in accounting interface: FI/CO interface: Balance in transaction cur

Hello Gurus-

We are on ECC 6.0 and we are having a problem with a few billing documents. Below is an example of the error we are receiving with several billing documents via VXF3:

Diagnosis

The balances in transaction currency must be zero for

logical transaction when transferring to the FI/CO

interface. A balance of " 1.75-" "U

was determined for the logical transaction "".

System Response

The FI/CO interface does not process any transactions

have a balance in transaction currency other than zero

Procedure

This is a system error of the calling application.

I have checked CMOD, account determination, OB09 and the G/L's FS00. The billing docs are in balance. I have someone checking out the interface to FICO in the meantime but I am hoping that someone can help me understand what the issue is? The billing document is in USD. This is not an inter or intra company billing document.

Thank you!!