Error Netweaver Gateway RFC call ended with "Communication Failure" exception, the types match, but not the length

Hi Team,

It`s vert complecated issue.

i run http://<IP ADDRESS>:<PORT>/sap/opu/odata/sap/ZHR_VF_RCV_SRV/PurchaseOrders('4500000215')/PurchaseOrderItems

Error List

1) RFC call ended with "Communication Failure" exception (Call of the function Z_GET_PO_ITEMS failed; a field should be assigned to the parameter PO_ITEMS - the types match, but not the length).

2) <code>/IWBEP/CX_SD_GEN_DPC_TECH</code>

when i run web service then getting above error message. i did not usderstand whats a problem because ERROR LOG also not working.

if i run below URL from browser getting below error message

http://<IP ADDRESS>:<PORT>/sap/opu/odata/sap/ZHR_VF_RCV_SRV/PurchaseOrderItems('4500000215')?$format=xml

<error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata">

<script id="tinyhippos-injected"/>

<code>005056A509B11EE1B9A8FEC11C22378E</code>

<message xml:lang="en">Invalid key predicate</message>

<innererror xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata">

<transactionid>7F6E02E42C3BF1469C3B000C29845429</transactionid>

<timestamp>20140703045714.2460000</timestamp>

<Error_Resolution>

<SAP_Transaction>

Run transaction /IWFND/ERROR_LOG on SAP NW Gateway hub system and search for entries with the timestamp above for more details

</SAP_Transaction>

<SAP_Note>

See SAP Note 1797736 for error analysis (https://service.sap.com/sap/support/notes/1797736)

</SAP_Note>

</Error_Resolution>

</innererror>

</error>

guys please guide me. its very high priority.

Regards

Pankaj Kamble