Give us some more details about how you're setting it up with Toast. Open the advanced drawer to the left of Toast (the blue & white button to the top left) & tell us what you have it set to including which options? There's 2 quality options, one standard & one high. And which ones you have ticked.

Are you sure it's a dvd-r & not a cd you're putting in. And you clicked dvd to the bottom far right on the Toast window .. sorry but I need to ask the basics. lol