I had the same problem with my Averatec 6200 that has a QSI DVDRW SDW-042 drive and it is not a driver problem per say - it's created by (many different) certain software installations and/or upgrades including XP & Vista and some times even when certain programs are uninstalled (I.E. Nero, Roxio, etc.). I've done my homework and I've seen the Code 39 and many other similar problems (failures) created with this drive that all have the same solution. Follow this link and do (#1.) fix in the registry - worked perfectly.
Obviously, this failure to load the driver(s) is created by these two registry entries:
Whenever these two are modified - the problem is created with the DVDRW (system cannot load the drivers properly).
I've tried it a few times now with the same results - and I was sure after a few searches that others would be experiencing the same problem.
Hope it works for you...