50x CDRW's?....I take it that they ae just CD-R's yeah?
It could be on it's way out, CD-Writers do have a limited lifespan for burning, if you do some intensive stuff with it, it can only lst a year or so.
But on't be put off getting a Lite-ON, they are damn good burners as you probably have found before this problem happened, I had the same drive as you and gave it to a friend when I changed to my 48x12x48x Burner....very satisfied.