That sucks dude.
Are you sure the little piece of plastic that surrounds the lens isn't the problem? The plastic is probably raising the CD too high for the lens to read. Unfortunately, it's very difficult to set properly back into place if it's been moved for any reason.
The HOP-M3 you installed should be fine if you got it on the metal rods and the gears line up, I'm talking about the little, free-standing cover around the lens that you had to remove during your installation.
I haven't looked at the piece for a while, but IIRC, it anchors to the board in three or four places. When you have time, open up your Duo again and carefully reattach the piece. Sometimes you'll think you've done a good job and it's all locked down but one corner will still be raised ever-so-slightly. In that case, keep reattaching it until all of the anchor points are perfectly flush.
It's also easy for that piece to get bent. I think someone recently posted that they just took the piece out and everything worked fine. Good luck.