so you had a working jtag and instead building a new jtag image for 16197 you tried to do a normal ms update from disk
?
we need more info! has the dash updated at all? is the efuse resistor removed? are you using a flashed or spoofed drive with it?
at the end of the day if the jtag still works then you need to build a new 16197 image
i guess you didnt mod it so if you dont have a nand backup or a external programer then you will need to dump the nand with one of the homebrew nand tools made for 360 then take the cpu key from xell and use these to build a new 16197 freeboot with the newer dashlauch and flash it using the same apps
google will help you find a good tutorial for this
if you have killed the jtag with a ms update then all you can do for now is make sure the nand and drive fw is stock+correct as the update may need to flash the drive so if you have a samsung instead of a liteon that came with it then it will fail the update as it cant flash a samsungi with new liteon fw
it does sound to me like the jtag is still ok