I've seen both errors in my experience with toast.
To "VeganBryan": the only time i saw that kind of error, my dvd-rw drive was beginning to head south. It completely failed 3-4 days later and i had to change the whole drive. I hope this is not your case and it is just your drive going crazy once.
Edit: have you ever been able of burning a dvd disc with toast? If the answer is no, try again burning a dvd with the finder and then check if the contents are all readable. If the content is alright, you got a weird incompatibility software-wise with toast (but i am very doubtful it is so). Otherwise you probably have a defective drive.
To hamish holmes: i had that errors a few times in the past. I don't know if my diagnose is right, but since all the times it reported such an error i was using cheap media, i would think it is because the media is faulty. Everything's should be ok hardware and software wise, so don't worry too much about it.
Edit: if the error persists or it is very frequent, try with higher quality media (Taiyo Yuden are my favourite brand when it comes to quality media)
