Get software here and flash your LG U880 with those files (in flasher set EFS erase).
After phone is flashed power it on with some not accepted sim. Type 142358#*# and after press red button, now phone will reset and accept sim.
Write down the above number behind the phone cos u need to enter it everytime u change different sim card .
You need to install USB drivers for the phone and properly connect it with the pc before you flash it.
good luck