All right. First of all, I'm sure you've come across a problem similar to mine in the past, as Matshita-related troubles are filling forums as of late.
In any event, I'll try to be as detailed as possible:
I've been using a Toshiba Satellite A-105 laptop with a Matshita UJ-841S DVD drive for about two years and a half now. The first year or so, everything worked smoothly: I could read and burn both CDs and DVDs with no problem whatsoever. About a year ago, I noticed it could no longer read DVDR, DVDRW, CDR nor CDRW. It still could (and still can) read DVD movies and music CDs perfectly, as long as they are not home-made copies. I haven't tried burning anything since then, pretty much because I have no way of reading whatever disc I burn.
The error I receive when trying to access the drive refers to an "I/O device error".
I've tried most of what's said in several forums, including: deleting those upper/lower limit entries from the registry; uninstalling the drives in the device manager; uninstalling all virtual drive/burning program I had; changing those DMA/PIO settings in the device manager; modifying my laptop's "hibernation" settings; and even modifying the CD/DVD drive acoustic silencer settings. My drivers, to the best of my knowledge, are up to date, as is my OS (XP SP3).
I went to a couple of IT shops and they told me I had to replace the drive. I wasn't too satisfied with the answer, because I suspected it was not hardware-related, however bad Matshita drives are.
Just out of curiosity, I tried to used the drive in Safe mode, and, needless to say, IT WORKED (pictures were choppy as hell and devoid of sound, but at least the drive could reach the data).
So, unless I'm wrong, this HAS to be software-related. Any idea on what may be causing it?