Both the Asus and Artec support DL (the Artec doesn't specifially say so but it does say "reads DVDs up to 16GB per disk" and AFAIK, DS/DL is the only way to get 16GB/disk).
Try cleaning (if you don't feel comfortable tearing into the drive like I do, you can get a cleaning disk at most of the big box stores - preferably one that uses a wet cleaning method) the drive and at least some of the other steps I mentioned before storming off to buy a new drive.
.bh.