This happened to me yesterday as well, I was about to restore apps using TB but the phone frooze and then anything made it boot. I don't know how Exactly I solved it but all I did was:
1.- Flash TWRP v3.01
2.- Wipe all the phone, including system, data, cust and internal sd
3.- From within TWRP flashed STock boot and recovery for 118CN FW.
4.- Placed 118CN UPDATE.APP in external sd/dload
5.- from within TWRP still, rebooted the phone to recovery.
6.- The phone started to flash the update from external SD.
7.- It succeded to flash files but couldn't mount /sdcard so I repeated steps above once more
8.- from stock recovery wipe/factory reset
9.- Tried the update again and voila! Phone succeded and booted just fine... Now it's been running with no issues since 2 days
I was running 118CN FW and a test kernel with some "non tested" or unstable features which I think forced the phone to frooze and then the data corruption...
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LG Optimus G - [ROM] PAC - 4.4.2 [KERNEL] Matrix Linaro Kernel!