Fail to recognize Rosettanet pip

I have sent a 3A7 to my partner , and my partner get it and reply ACK to me. but the system fail to recognize it and the ACK is inserted to TN as unknown message. The error message as follows,

formattedError,
Error trapped in service: wm.ip.rnif20.trp:getBodyParts
Error: NoClassDefFoundError
Occured at: 2008/05/24 12:14:29.296
Service Call Stack:
wm.ip.rnif20.trp:getBodyParts
wm.ip.rnif20.trp:unpackMimeData

RNOError,
rnif20.trp:unpackMimeData(): Error trapped in service: wm.ip.rnif20.trp:getBodyParts
Error: NoClassDefFoundError
Occured at: 2008/05/24 12:14:29.296
Service Call Stack:
wm.ip.rnif20.trp:getBodyParts
wm.ip.rnif20.trp:unpackMimeData

serviceName,
wm.ip.rn:recognizeRN

Thanks,

Crane