Thank's for your concern for this symptom.
Now, the error have been not raised for several days, so I cannot make sure the description of error now, but I guess it was software broken error, not thowing exception.
In addition, the error is occured at NeroDone() from time to time, and it seems to be depended on test set - even though the environment of each set configuration is exactly same. That's too abnormal. I can't find any clue.
Can you get any hint?