DVD - next track button works, Blu-Ray - Next track button unavailable

hi all, I created a DVD and a BluRay in exactly the same way but when I push the skip to next track button when playing my playlist comprising of 5 chapters (5 different timelines) it works with the DVD but not with the bluray.

I haven't set any 'overide' as I'm not sure what this is, have just specified an end point of each timeline (which obviously gets ignored when playing it as part of the playlist but does work when playing selected timelines from the scene selection menu)

Does anyone have any idea what I'm doing wrong and why the bluray doesn't enable me to skip to the next track during playback?

sorry, CS5