Hi,
The way I understand it, the sequence should be:
BAPI_XMI_LOGON
BAPI_XBP_... calls
BAPI_XMI_LOGOFF
I'd check what the BAPIs returns are; the message seems to indicate that the logon was not successful (before BAPI_XBP_JOB_STATUS_GET call). Maybe the logon expires after some time...? Sorry, I'm absolutely clueless about the Java connector stuff...
cheers
Jānis