strange sequence playing

hi,
i have strange thing - maybe you can help me to solve it.
i make seq, work with it, cut and paste, do usual things - nothing specially or extraordinary, and suddenly when i press PLAY only few sounds from my bank are playing, or not in the full lengh of seq, like i turned on mute function. but i didn/t. i dig most of the screens and don't see a thing, it all seems that other sounds should be played, but they dont!
do you know anything about it?
i have latest official os

In Program Mode are your samples set to POLY?

some of them are poly some are mono - thats not the case.

Do you have the memory expansion?

yes. and hd with 80 gb one from the recomended by akai