iPhone will not restore and is stuck on low battery screen?

[khenderson]

I let my iPhone 3g's battery run flat a few days ago by accident, since then I have not been able to get the phone to recognize it is being charged. I plugged it into my mac and put it in DFU mode (i think), but my iTunes popped up with 'Unknown error, this iPhone can not be restored'. Now when ever I try to get it into DFU or restart it nothing happens except the red flashing no battery sign shows?