Motobat:
You've probably already done this... but check your MIDI Note assignments for each voice. I recently sold my R8, but it was absolutely NOTORIOUS for dumping the MIDI Note Assignments data everytime I blew a new set of patterns into it's memory. For some reason, it interepreted an upload as "reset all notes to their default MIDI assignments", which meant that even though the pattern/song played fine from the R8 itself, by the time I THOUGHT I had sequenced the data and tried to play it back... no joy.
Roland drum machines suck - and they make the best drum machines in the world!
I still believe the R8 is the best-sounding drumbo on the planet, but I just couldn't take the programming-intensive yuk that came along with it. I've gone back to my TR-707 - at least I could program it and rely on it to work the same every time!