Had an interesting thing happen at rehearsal last night. Have a show tomorrow we were running thru the set. Pull up the first of two presets needed for the song. Go to switch to the next preset and... nothing. No sound at all. A quick investigation shows that that entire preset is completely blank now. Everything else is fine, just that one disappeared. I'm hoping I backed the unit up since creating this preset (it's a new song were working on) so I can load it at the venue before the gig. But any idea what happened in the first place?