Try switching the transfer mode of the DVDRW from DMA to PIO or Vice versa (depending on its current state)..
Right click my comptuter ->manage-> IDE Drives (Im assuming that your using an IDE DRDRW) .. NOw it gets tricky.. there will be a few options primay/primary, secondary/secondary, etc.. If you know which IDE port your DVD Drive is using, great, if not, either follow the cable in your comptuer to see if its the primary (blue) or secondary (black) and then which lead off od that cable, the farthest, or the closest (the fathest is the primary on THAT IDE cable) ..
Then, switch the mode to the associated cable..
(Ill try to find a guide that might be clearer)
Hope that helps, I was having the same kind of trouble untill I did that.. I even baught a new drive..