I'm not sure if you are saying that the disc stops playing (actually stops spinning), or if the graphics go away and the music continues.
Please forgive my pickiness.
I have had the problem where the player plays the music on a blue screen, but once I decided to burn my "outside play" discs at 6x the problem has gone away. Also, this problem would occur at the outset, not part way into a song.
Have you tried switching FROM the mitsui's?
Have you played these discs successfully in any non-computer players??
Was your burner tested and certified for cdg??
Have you played the files all the way through successfully as files using Microstudio Play? (Making sure that the files are extracted properly by the cd-rom)
Do you import tracks or do disc-copy?