This is very wrong. Has it ever worked before? With dual-layer media?
That seems really weird.. It had worked before a few times, mostly with CloneCD. ImgBurn worked once or twice, I believe.
Anyway, thanks to LIGHTNING's suggestion, I grabbed a new burner (the Pioneer DVR 116D) for about $40 today, and I've had 10 for 10 successful burns!
Big thanks to all of you support people and devs of ImgBurn!