it's hard to help when we have no details. what happened prior to the phone going dead. was something installed? did you have problems before? have you tried connecting the phone to itunes and attempt to put in recovery mode or DFU mode?
I have the same issue (well.. my sister is having the same issue) It's a 1st gen 8gb iPhone. It was jailbroken and unlocked about 6 months ago (not ziphone) and it worked fine up until last week. She said that she witnessed the screen go completely white while charging on a wall plug. She then rebooted the phone and it came back up ok, but when she attempted to access the bottom row of icons, she could not.
The rest of the screen worked, just not the bottom (verticle)
The phone will not charge on a wall plug, or via USB on the computer. I've tried different cables and adapters, NO response. I've tried putting it in DFU, but the Apple logo never even appears.
No response from the phone when connected to a pc, wall or while holding home+sleep buttons.
The battery did not display any signs of failure, it held a full charge right up to the day it stopped working.