The error message indicates that this is a limitation of the DAQ device when utilizing synchronous events. Your declaration seems to be correct but the first error (-200979) is a result of using DAQmx_Val_SynchronousEventCallbacks as the value one. (ie. Synchronous events are activated) To possibly find a work-around to your issue, more detail is needed as to why multiple threads are needed for one DAQmx Task and what exactly you would like to accomplish.
I am trying to do the same thing with Visual Basic 6. If I set the Syncronous flag I get a -200077 error: "Requested value is not a supported value for this property."
Is this not supported with my SCXI-1600 board?
lnDAQStatus = DAQmxRegisterEveryNSamplesEvent(mDAQTask, DAQmx_Val_Acquired_Into_Buffer, _
mScansPerSample, CLng(1), AddressOf TCChannelsMgr_DAQNSamplesDoneEventHandler, Null)