I have ran the AHT and it give no indication that there is anything wrong with the Super Drive. Mine will read and write CD's all day long but if you put in a DVD of any sort it will just kick it out.
Firmware Revision: FM0S
Burn Support: Yes (Apple Shipping Drive)
Cache: 2048 KB
Reads DVD: Yes
CD-Write: -R, -RW
DVD-Write: -R, -R DL, -RW, +R, +R DL, +RW
Write Strategies: CD-TAO, CD-SAO, DVD-DAO
Write Speeds: 8x, 24x
Zap the PRAM and Reset the SMC, then try again. If no go, then contact Apple Service, iMac Service or Apple's Express Lane. Do note that if you have AppleCare's protection plan and you're within 50 miles (80 KM) of an Apple repair station, you're eligible for onsite repair since yours is a desktop machine. At least in the US. You'll have to check for other countries.