I've had a iPod for a while now since Rockbox 3.5 I think and although I've had it lock up a few times, it has been weeks between. Since yesterday with Rockbox 3.8, I've had numerous lock ups during playback or just updating the database both whilst on battery and whilst charging.
I'm hoping either going back to 3.7, going for the current build will fix it otherwise does it mean my iPod is on the way out?