The problem of multisession



I use this :
NERO_VMS_INFO *nvi = NeroGetVMSInfo(m_ndhNeroDeviceHandle, 0);
m_PreItem = NeroImportDataTrack(m_ndhNeroDeviceHandle,
nvi->nvmsiNumSessions-1, &m_ndWriteCD.nwcdpCDStamp,&pInfo, NIITEF_IMPORT_VMS_SESSION | NIITEF_IMPORT_UDF, &result,NULL);
NeroBurn(m_ndhNeroDeviceHandle, m_CDFormat,&m_ndWriteCD,
NBF_WRITE | NBF_CLOSE_SESSION,0, &m_ndProgress);

to make a virtual multisession data dvd.

when the nvi->nvmsiNumSessions== 1,they succeed!

But when I burn again,nvi->nvmsiNumSessions== 2 ,they don’t succeed!
m_PreItem = NULL,result = NIDTR_DRIVE_ERROR;

I use Windows 2000 , nero 6.3 and NeroSDK-1.05.
Help me please! Thanks!