memorex is the junk of junk...
firmware is sort of like the operating system that is inside your drive. it tells the drive how to write. when new media comes out, a drive might not have a write strategy for it and will have to use a generic one, but a subsequent firmware update will give the drive the ability to write this media well.
your firmware can be determined using nero infotool
visit the sony website and find the support page for your drive. click "downloads" or "updates" or whatever similar link there is to check for newer firmware than what you already have.
if you find that your firmware is out of date then check the firmware subforum here on cdfreaks for some tips for flashing your firmware before you go ahead with it. there are some precautions you should always take while flashing firmware.