You have a problem with the drive, not the disc at this point. The hardware(drive) reads the disk ID and reports to the software the type and capacity of the disk -CD vs. DVD, +R vs. -R, RW or not, etc. Even how made it. Toast will even let you click a link to a web site that tells you what people think of it.
It doesn't know how to read the disk ID for CD-R's now so unless you got the 3 year Applecare you may be out of luck.
However unless you really need to do a lot of on the road burning, even if it did work, because the performance is so annoyingly slow, I'd suggest you buy the cheaper LaCie FW DVD burner, the Porsche model as you don't need the software.
Burning DVD's at 16X you realize how slow the 1-2X PB models are. And they offer DL DVD burning, lightscribe labelling and you will notive extermely fast CD and DVD ripping speeds. I do travel a lot and were it not for my plan to get a macbook pro I'd carry a DVD burner with me.