Fiddling with the pot will most likely return your Duo to working order, considering that it wasn't working 100% before running any CDRs. If not, then the new laser you installed might be defective, which wouldn't be the first time that someone ended up with a lemon. Good luck, it'd be a shame to hide such a sexy machine in the closet.
Dude, CDR's might not be the best thing for your hardware. I'm not a technical guru, so I'll let those folks explain why (something about the data tracks on a CDR extending beyond the limits of the laser's track?)...
A properly ripped disc shouldn't require an overburn, as the originals aren't that big; I believe the problem with CDRs is their lower reflectivity.