Well...
In another post (no real need to post in multiple forums as most people read them all) you said you uploaded music. If you press the down button 3 times after boot you should start playing all music on the player. Do you get any output on the "home" RCAs? As I said in reply to your other post, hooking up Hyperterminal and getting the boot log might be useful. If you have a 2.5 allen key you could remove the fascia (unscrew the four bolts, remove fascia, pull off, the knob straight out and remove the blue panel). Inspect the fill nipple of the glass display - located at the lower right of the display, just by the knob. It's a small glass stub that if broken means the display is dead - so don't go breaking it while inspecting!
As to returning for another unit, I think you'd be better off (and just as quick) contacting the empeg guys in England (carsupport@empeg.com IIRC). If broken they'll arrange for overnighting it back and forth - US owner have been known to send it off on day one and have it back, fixed,on day three...
/Michael
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/Michael