ok...need a little more detail.
how does this disappearing manifest itself? are in you instruments? sequence? do you hear a sound when in, say, instrument, but it disappears when you switch over to sequence?
if you go to instruments, hit patch edit and then partial edit and then samples edit and there is no file there anymore? what about if you hit sample list when in sample edit? can you see the samples in the sample list? what is the output of patch assigned to?
or are you in sequence? is there a patch listed in output assign?
do you hear a sound when hitting a pad, but when you start a sequence playing it "disappears" the sound? might be a patch change recorded.
If it isn't an issue with this two areas I'd hit the mixer button and have a look settings there.
