NIkon SB-800 not functioning?

My Nikon SB-800 isn't working. The illuminators on the front are always on, however the lcd screen isn't turning on. I've changed the batteries. Left it for 24 hours but its still the same. I need to use it in two hours for a band promotional shoot. Any ideas?

-J

Added (1). I have tried firing it as a test.
Once the batteries are in and i've closed the hatch, the illuminator turns on and it charges and flashes. (even though i have not turned it on).It won't fire on demand though.

This is why you have backups of every important piece of equipment…
Have you tried firing it at all as a test or on camera?

Is the hotshoe making good connection? Have you tried cleaning the contacts?

Someties, I also have proles with my canon flash, for no obvious reason.
I just turn everything off, disconnect it, clean the contacts, and it will in most cases work then.
I'm not sure, if its the reboot or the cleaning. And sometimes, it just has a bad day, and will not work at all.