UD's "backup in the car" has me thinking. I currently use live-midi-only in my performances and my backup to my arranger keyboard's HD is my laptop computer, which can either act as a midi player for my keyboards or use it's soft synth to play the midis itself. But I don't normally take the laptop to the gig without reason, so I'm relying totally on my arranger during the actual gig. I think that after the holidays I will make backup MP3's of my most-needed accompaniment and store them on my Creative Labs Nomad MP3 player, which I usually keep in the car anyway.

BTW: I use Sonar 2.1 - it is very stable.