So I have the same issues others are having with not being able to update on my rooted N10 except, I can't go into recovery.
About Me: Rooted Nexus 10> Running Stock JB 4.2.1>
When I hold down the power and down button I go into the bootloader and it says "Downloading... Do not turn off target!!" and it will just stay on this screen.
I can't toggle anything, up and down buttons do not work to go into recovery, reset bootloader, start device etc..
But I can hold the power button down and then restart the device and everything works fine. How do I go about this?
My only thinking is that I am going to have to go into ADB, but I'm not even sure if that's going to work.