I am sorry to say I have recently discovered the very same problem with my LG GSA-H55N. It will play any ‘copied’ disc and only select purchased disc’s. Even ones it played previously.
At first i thought it was region coding mis-match between the new drive and the RH177 but I have reflashed the ROM’s to be region free for both the player and the drive but this had no effect.
I have even set both to ‘Region 2’ but still the same “navigation fault” on certain ‘Genuine Discs’ with no rhyme or reason as to why. I have looked at the Region Coding of the disc’s and there is no correlation there either. It will play Region 1 and Region 2 on some disc’s and then not others.
I have tested my LG GSA-H55N on my PC and it will read all the discs just not when its installed in the RH177.
The last thing I was going to try to re-intilize (restore to factory settings) the player using the controller but this will wipe out all the wife’s recordings and she wasn’t to happy about that. So I haven’t done it yet.
I was going to do this as it has to be an issue with the player as the drive works fine in a PC so the player is the only thing left. There is a lot of BIOS around and I have tried a few of them with no effect on this problem.
Any idea’s or solutions you can find would be gratefully received!
Workaround - Copy the disc’s using DVD Shrink and they will play no problem