Toast has been passed around like a bong at Woodstock. It used to be the absolute best app to burn CDs and DVDs, but the last few years it has been buggy as all get-go.

As to your problem, I don't know what the solution is - but I will tell you that setting the SPEED of the burn to the ACTUAL speed of your SuperDrive tends to fix a lot of the problems I was having with it. By default, I believe Toast sets the speed to "best." Leaving it set to the default resulted in an unreadable disc, a failed lead-out, or a failed verification nearly 100% of the time. Changing it 8X fixed it nearly 100% of the time for me.
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