Hey,
I WRESTLED with my modded serial cable that I built for the lite-on that I made through yaywoop's tutorial. I was powering lite-on drive through the 360, and the WHOLE reason why I couldn't get that stupid key was because I wasn't getting the dvd tray to stay half-way open when I turned the 360 off and then back on. What I had to do was:
1. turn on 360
2. eject the drive
3. press the same eject button to close the drive.
4. eject again
5. close again the same way, but this time while closing, unplug the DVD DRIVE POWER CONNECTOR while tray is closing (drive should remain half-open when you unplug the power connector)
6. Press the power button to shut off 360
7. plug dvd power connector back in
8. turn back on 360
All done AFTER PC booted to DOS. I suggest doing the dos method (run dosflash to identify sata port before steps 1-8, and dvdkey xxxx AFTER all 1-8 steps have been achieved; xxxx is the sata port found via dosflash). good luck.