Attention CECT P168 owners. If you are in engineering mode NEVER NEVER NEVER select or turn on"High Speed SIM" option.
YOU WILL BRICK YOUR PHONE!!! This is a serious firmware bug that is not well known. I happened to find this by doing a deep search on Google where some owners decided to do this. Whats happens if you do select this option. A countdown begins and the phone will say "shut down in 3 sec 2....1....then shuts down. And it is never possible to reboot the phone after.
Everybody that has pressed the High Speed Sim on has had there phone shut off and could not restore the phone. There is no such thing as a high speed sim all of our sim cards are either 32kb or 64kb.
the "only" way to fix your phone is to do a complete re-flash.