More experimental results:

On my empeg, I dragged my iTunes folder over whole, then I have a couple soup playlists made with jemplode. If I directly select the iTunes folder, skipping the soup lists, the I end up with one fewer tune in the playlist, and the empeg successfully remembers its playlist across reboots. Fascinating.

Otherwise, I haven't been able to make a dent in the pop after 18-or-so seconds. Even if I select a much smaller playlist, the problem still occurs. The back-button issue likewise persists. If I press "back" when the song has only been going for a few seconds, it works fine. If I wait until I'm a minute into the song, after which presumably the beginning of the song is no longer in cache, then the back button makes the empeg stall. Hitting forward and back again is the current work-around.

Paul, do you experience similar problems with your massively loaded empeg? Are you using a MkII or a MkIIa?