You have a locked bootloader, because you are using LG's official ICS V30C ROM. It has a locked bootloader, if you try to access the recovery from within the ROM, it gives that security error (sometimes). I will suggest following jockjoint's thread
to get your OB an unlocked bootloader.
It will help you unlock the bootloader and then also flash a compatible version cwm, because not all versions are working with the new V30C. Once you finish following the method prescribed, your phone will boot into cwm, flash su.zip then and you'll have root. Then flash a ROM+kernel of your choice after 2-3 wipes. (IZSv1.1+diana3 v0.5 = my personal favourite).
I know, if you were trying to backup your ROM, it was because you had some important data to preserve. But there's no way you can get your phone working and preserve the data at the same time, unless, you are one of those, one in a billion lucky ones who manage to bypass the locked bootloader and get into the ROM because you were pressing all stupid combinations of hardware keys one can imagine of, when the phone was booting up. If are one of those lucky souls, you can use UPK (Upgrade KIt) to unlock the bootloader and then just flash a compatible cwm version (part of UPK itself) and you are good to go. UPK is a sticky in the OB forums section on xda. Otherwise use 'Search'.
Press 'thanks' if I helped.