You should respring your device. Go to Settings > General > International > Language > change the language to a primary language which you can understand. The device will respring and hopefully the problem will be solved, you can change back the language.
Did you install SemiTether package? I guess NO. Ok do this.
Install this source :-
thebigboss.org/semitether
Open the source, install this package SemiTether, after installing open this app from homescreen and close it. Now you can switch on cell phone after turning off but you ll have to boot tethered to use jailbreak apps.