Download and install the latest firmware upgrade for the drive. I had to do this for my Plextor 708A DVD-burner.
Also, how old are the CD-ROMs the drive won't recognise? The dye-layer may be slowly deteriorating - it happens, and some environmental factors (heat and humidity changes) can accelerate this process. Cheap disks have lower-quality dye layers than the more up-market ones. I use Verbatim CD-ROMs and DVDs and refuse to use any other brand. My info is too precious to entrust to cheap media.