Well you could have a motherboard issue. However, this may be a dumb question but have you put the lens ribbon cables back in the correct way? The larger wider cable should be inserted with the contacts facing outwards away from the center of the CD drive.
Also, to test the CD drive just hit the play button on the top to use an audio disc. This will at least let you know if it is a CD drive issue or a docking station/system issue.