errors during import of invoices

[prema]

hi everybody
i am importing invoices using Open Interface Program but im getting problems at Project level,i.e the lines associated with projects
i have debugged and the error is (PA Flexbuild 6) PA_TRANSACTIONS_PUB.VALIDATE_TRANSACTION Failed :Insert Rejecti
on
PA_TR_EPE_TASK_TXN_CTRLS
(Insert Rejections 1) Insert into AP_INTERFACE_REJECTIONS, REJECT CODE:PA FLEXBU
ILD FAILED

i have searched in the ap_import_invoices_pkg but could not find it
can anybody help me plz