Exception condition "FAILURE" raised., error key: RFC_ERROR_SYSTEM_FAILURE

Hello,

In my Web Dynpro Java Application, I need to execute the BAPI_PO_CREATE1 RFC Function many times. When I executed it at first I haven't errors, but in the second one and other times i have this problem:

<b>Exception condition "FAILURE" raised., error key: RFC_ERROR_SYSTEM_FAILURE</b>

I go to ST22 in R/3 system and i encountered this exception:

<b>Exception condition "FAILURE" raised</b>

and the exception is marked at:

<b>CALL FUNCTION 'MEPO_DOC_ITEM_GET'

EXPORTING

im_ebelp = po_item_number

IMPORTING

ex_item = ex_data

EXCEPTIONS

failure = 01.

IF sy-subrc NE 0.

<u><i>>>>> RAISE failure. <<<<</i> </u>

ENDIF.</b>

I check the data is entering the Bapi, and these are always equal.

Please, if you have any information about what can cause this problem i would be very grateful.

thank you very much.

<i>Nahuel Romanello.</i>