Problem while IDOC processing interfacing wih SAP 5

When “INVOIC” data is sent from SAP system, the error log in webmethods shows the following message:

“Input values do not contain IDOC control and data”
No Routing rule is generated for “INVOIC” message type either.
The data can’t be seen in the Transaction store either.

The Status Monitor for ALE Messages" in SAP also reflects the same message :“Input values do not contain IDOC control and data”

SAP Outbox for INVOIC shows the message :
Data passed to port OK
IDoc sent to R/3 System or external program
The INVOIC data can’t be seen in Webmethods SAP adapter!

I am working on the SAP Version 5 system.The data being sent from SAP is in Non-UNICODE format.Could it be causing the problem?
The same scenario, works while using SAP 4.6 Version.

Can anybody suggest,the solution.Highly appreciate a quick response!!
Thanks in advance!!