I too have an LTN-526S and tried to upgrade the firmware. I went to the site mentioned in the links at LiteOn and downloaded the correct firmware file ( 52SYS0N.zip ) , extracted, and ran it. The error stated "Drive model doesn't match!!!!" I have unplugged the other CD-ROM in the computer and have verified that I didn't misread the label on the drive and that it is the "Master". Mine was not OEM but came in a box, etc. that I bought separately.
The basic problem I am trying to solve is that under XP SP2 whenever I put a CD in the system doesn't see it the first time. I have to put it in, eject it, and then put it in again. Once I do that all is well but of course a pain. I assumed that a firmware upgrade would do it. Any other ideas? I really don't care about firmware if I can get the problem described to stop.