getStatusString error

Hello,

Sending ebXML message through Trading Networks to external partner. Message acknowledgement returned contains error in Transaction Analysis - Activity Log:

An error occurred invoking the processing service wm.ip.ebxml.rules:processAckMsg for this document. The original error was com.wm.app.b2b.server.ServiceException: wm.ip.ebxml.trp:getStatusString: missing {1} [ESEBXL.000000.000002] at com.wm.util.LocalizedException…

Any ideas??

Thanks
John