[Sprint LG Optimus G] Mitch Connor:
I had a similar problem as you. Upon getting the phone I rooted and used the FreeGee app from the Google Play store to unlock the bootloader. Everything seemed fine and dandy, until one day when I let my phone's battery drain completely. Pluggin it in to a wall charger resulted in the failed boot where the LG logo flashes before going to a blank, but backlit screen. Luckily, the first few times this happened, through a combination of quickly plugging and unplugging the usb cord and holding the volume up+power button, I could get it into recovery (TWRP). Then a simple cache & dalvik cache wipe, and the phone would boot up as if nothing ever happened. Very strange.

Well yesterday this happened again, however, this time there was no getting the phone into recovery. My previous methods of button mashing and plugging and unplugging weren't working. So, I decided to bite the bullet and use LGNPST to get back to ZV7. Now, like you mentioned, this failed boot would automatically happen, without pressing the power button to turn it on. So it was difficult to get the phone to stay off. I found that with the phone unplugged, if you continue to press the power button until the blank backlit screen turns off,

AND

continue to hold the power button for an additional five seconds, the phone would stay off and not auto power on into the failed boot.

Once I was able to get the phone to stay off, I pressed the middle of the volume key to depress both volume up and down, and then plugged a usb cord that was attached to my computer. This powered on the phone into download mode. Following the LGNPST guide I was able to get to around 67% complete before my phone turned off and an error message flashed on the computer screen telling me to power cycle the phone and reconnect. Well, the whole 67%/85% LGNPST failure is apparently common and not indicative of an actual failure; HOWEVER, my phone became completely unresponsive. It wouldn't power on at all. It didn't matter if the usb was unplugged or connected to the computer or wall charger. So, I was forced to unplug the battery. I followed

this

tutorial and successfully disconnected and reconnected the battery cord, and the phone shot back to life. It even booted up into the factory stock ZV7 rom. I guess that LGNPST was successful. It looked like I was on my way to returning my phone to breezy's deodexed ZV9 stock rom that I was previously running.

I went ahead and re-rooted, ran the FreeGee app again, and rebooted into recovery. Then I made a backup and attempted to flash my new rom. Now, I think this is where I royally screwed up. I was pleasantly surprised to see my screen layout and all of my settings still intact after LGNPST back to ZV7 and thought I could just wipe the caches and ignore the factory reset and system wipe before flashing. Perhaps it was this, but part of me also thinks there might be something wrong with my battery draining extremely fast in recovery.

I proceeded to flash and all seemed good, but rebooting resulted in the LG logo failed boot that we have already discussed. So, I went ahead and repeated the LGNPST-re-root process numerous times (switching to the freegee 0.5 batch file instead of the app). Everytime after the first initial restore, I could never get my phone to enter recovery. As soon as I rebooted after using freegee, the phone would be soft bricked again. Sometimes I would get the LG logo thing, other times I would get the dreaded alternating flashing red notification light and soft keys. A battery pull was usually required in these circumstances before I could get back into download mode to start all over.

I was about ready to give up when I took to the LGOG irc channel. That's when Xboxfanj stepped in and helped me out IMMENSELY. Over the course of several hours, he walked me through flashing some partitions in ADB. At times it seemed like there was no hope and that I should have just returned the phone, but he failed to acquiesce, we pushed forth trying a couple of other bootloader options. The new bootloader appeared to have fixed the phones erratic behavior with powering on and off, but I had no rom to boot into and no recovery. Xboxfanj recommended using fastboot to flash over a recovery. Once in the new bootloader screen my Windows XP machine detected new hardware and wanted some drivers. I attempted to use the

[ADB/FB/APX Driver] Universal Naked Driver 0.72

, but XP indicated that I was missing 'winusbcoinstaller2.dll'.

I grabbed winusbcoinstaller2.dll from

here

and all was good. Fastboot recognized the phone, I was able to flash recovery and subsequently boot into recovery. From there I reformatted the system, wiped data/factory restore, wiped cache, wiped dalvik cache, and flashed breezy's ZV9 deodexed rom.

Fortunately, after around 7 hours, I am happy to say my phone is back to being rooted, unlocked, and running ZV9. It powers on and off properly and can get into recovery without a hitch. I'm still curious what will happen if I let my battery drain completely. Perhaps I'll try it some time this week. I'll be sure to post back here if/when I do that. All in all, it was a harrowing, but educational experience.

Anyway, just wanted to give a big THANK YOU to Xboxfanj! You really are the man :good:. Thanks for your patience and determination.