hmmm...i would say it was probably because of either:
1) NOT unplugging the white ribbon cable for the laser.
2) Updating the dashboard after flashing LT.
both of these are not proven one way or another, but are possibilities of why you are receiving an Open Tray error.
you can probably still pot tweak it (i like 3.36) and it will work fine.....worse case....new laser.
please see this post for flashing the 74 LiteOn: