Recently my new (within a year old) Pioneer DVD burner stopped erasing my DVD-RW disks. It would appear to erase them, but when the disk was re-inserted in the drive it still had the same content. And occasionally I would get the
message, "The device failed to calibrate the laser power level for this media."
In researching this, I found that there was a newer firmware than the original Apple firmware it came with. The problem was that the firmware was contained in an EXE file and Pioneer didn't bother to include any installers for the Mac. In searching I found that the EXE file could be opened and the firmware files found using Stuffit Expander. That got me the firmware files, now what?
OK, there's a flashing program that has existed for some time. The program is a terminal command called "DVRFlash." The usage of this program got me nowhere, since it refused to clobber the Apple OEM firmware. But by looking further, at the bottom of the DVRFlash webpage there is DVRFlashX, a GUI for OS X. This program was able to easily flash the firmware.
After a reboot, my Pioneer DVR-109 was upgraded to firmware version 1.58! Not only that, I could erase my RW disks again! Yeah!
If you have problems with your optical drive, this is one method you might try, assuming that there is a firmware update for your drive.