I have had success backing up two previous types of Karaoke mixed audio vcds using the mixed mode CD in Nero 6.
However, I have another set that defies backup. I have tried Nero 6, Alcohol 120% (selected karaoke type CD+G), Plextor discdupe and Blindwrite 4. They all make a playable audio CD but there is no accompanying vcd video and subtitles. I have tried several dvd standalones and get the same thing. Each program sees 1 session, 22 audio tracks, 0 data = 700MB image size. I have tried checking boxes like reading sub_channels. No luck.
My drives: Plextor 8/4/32A; Plextor px-708UF; Matshita UJ-811 H100