Well being as it just turns on then off right away i would say 1 of 3 things the battery is dead,somehow you have wiped the startup files off the flash chip, not sure 100% how the update works in regardes to what it wipes when updating or you have some other hardware fault.I would try leaving it on charge over night, format a sd card on a diffrent machine and load the script folder on it try a custom frimware)and try again,last option is to remove the flash chip and reprogram it via a chip programmer (i am looking in to doing this but need to buy a donor unit to wreck for this)I guess it could be jtagged but need to know the jtag points.