I dumped Thousand Arms (U) yesterday and it appears to have a form of copy protection I haven't seen before. The disc is perfect, but EAC was reporting all errors on the audio track. With "Read C2" turned off the track dumped 100% quality.
I dob't know i this was used on any other games, but it might be something to check if you run accross a seemingly perfect disc with undumpable audio tracks.