[Q] Brick after lg mobile support tool and kdz update

Well it's not the first time i switch roms on my optimus 4x, but this time i've been banging my head against the wall for more than 6 hours trying to figure out what's wrong. So the phone was running CM 10.1 for about 2 months and i wanted to return to the stock jelly bean, i used the kdz update method exactly as shown in here http://xdaforums.com/showthread.php?t=2069723. I tried it a couple of times, and each time the phone reboots and gets stuck at LG boot animation. So i tried to use the official LG mobile support tool and use the upgrade recovery method, it downloads the firmware and installs it to the phone but the same happens, the phone reboots and gets stuck at the boot animation. I've tried the kdz method about 3 times again to ensure i did everything right, then tried the LG mobile support tool for a last time and just the same happens. Now i'm enable to open the phone. I can still get to S/W upgrade mode though. So i really need help here because i've tried everything i know and failed, i need to get my phone functional again ASAP. Thanks.

Thanks sPEADy, actually that was the last thing i did before going to bed and the phone started normally. Thanks again for your help.