Mac won't recognize my Sony DRX-830UL-T DVD burner

Hi,

I have successfully used this burner in the past, but for some reason now my computer won't recognize the existence of my burner. When I go to Toast and attempt to burn movies, it only recognizes the DVD machine that comes with the computer, which does not burn DVDs. I believe I have it connected right. It's plugged in, and on. the top cord is connected. Please any help you could provide would be great. Something always seems to go wrong when I try to make a home movie! Thanks!