Unexpected Error in AR_INVOICE_API_PUB.CREATE_SINGLE_INVOICE

Greetings - I am trying to create a "simple" invoice using the Create_Single_Invoice API.  We are on v11i.  I am receiving the following error from the API and can't retrieve any errors from the temp table ar_trx_errors_gt.
 
Error in AR_INVOICE_API_PUB.populate distributionsORA-01427: single-row subquery returns more than one row

These are the parameters I'm populating the tables with before calling the API:

l_trx_header_tbl(1).trx_header_id := v_header_id;
      l_trx_header_tbl(1).trx_date := inv_rec.inv_dt;
      l_trx_header_tbl(1).gl_date := inv_rec.inv_dt;