Any pointers apart from it locking up on the logo screen?Well, since the capacitors fixed the problem for me, I can't reproduce it for you any more.

But assuming that my problem was the same as Schofiel's problem, here is what I knew about it:
1) It was intermittent. Sometimes I would crank the engine and the unit would reboot fine. Other times, it would reboot to the logo screen and freeze there permanently.
2) It didn't seem to matter whether the unit was in sleep mode or in playing mode.
3) Removing and re-inserting the Empeg made it fully reboot and work OK. The only time that this seemed to happen was on engine cranking: When the voltage would drop but not go away completely.
4) When it froze, it would freeze at the logo screen and you'd never see the bootup text scrolling by (which usually came after the logo screen). Obviously, no button-pressing would fix it at that point.
5) It only happens on certain cars. On my GTI, it was fine, but on my 2000 Honda, it happened. I can only assume it's because of what was reported elsewhere on this thread: That Hondas use a high-RPM starter motor which draws more juice. Plus, my Honda has a bunch of electric/electronic stuff built in (factory security system, etc.) that all fires up when I start the car, and could be contributing to the voltage loss.
Tony FabrisEmpeg #144