I suppose you didn't finished the update in the correct way ?
Stopping halfway the proces make your device useless, sorry.
See the bootloader as the bios in your pc, it has the basic process inside to start all your hardware, the bootloader is written in I expect into a kind of an e-eprom
now this part is corrupted and won't start anymore. When it is realy an e-eprom I don't understand why it is impossible to downgrade it easy.
But now you took the hart out of your device, only a wonder will help you.
Anyway I hope there will be someone with another solution for you.
Aad - pe1agp