Usually it is an issue with ASPI layer and how burning software uses it, but sometimes also may be result of firmware interface. This is nothing critical but may be annoying.
The best approach to get rid of it is to update the ASPI layer (
http://www.adaptec.com/worldwide/sup...aspi_471a2.exe) and Nero to 5.5.10.15a or at least Nero ASPI Manager (
ftp://ftp6.nero.com/wnaspi32.dll) if that does not help (it should, at least it did for me) try updating firmware.