The ASUS sdre-08d1s-u is not burning cds. Common problems? fixes?

I have the exact same unit, and after about 100 burns the little guy gave out on me. If it isn't burning, I would recommend going into your device manager on your computer and checking to see if your USB hub is functioning properly. In that doesn't work, or you don't find any issues, try plugging it into a different machine to check and see if your computer is the one at fault. Often, the motor itself is the damaged unit, rather than the internal workings, so the computer says it's working fine, and lo and behold, the drive won't work. If that doesn't work out for you, then unfortunately it sounds like you're out of luck, and it would be cheaper to just purchase a new one.