[LG Thrill 4G] the ManaWhoney:
When it says waiting on device try pulling out the usb and then plug it right back in. I use to have to do that, but if that doesn't work then it may be a driver issue.

Maybe start the tool and when it says waiting for omap4430 device, hold down vol+ and plug in your phone but don't let go of vol+. Pop in battery like normal and it should boot you into download mode. See if that helps get your LG Cosmo driver to install, though it should install as LGE CDMA USB SERIAL PORT. if that doesn't happen, as a last resort uninstall all LG mobile drivers, reboot cpu, download the files from step 1 and step 5 of this post---> http://xdaforums.com/showthread.php?p=39269819 (bag of goodies and wkparks 1.21) Turn off your anti virus and windows defender before doing anything. Once thats done unzip the two files mentioned above. Run the omap flash installer and re install both Sets of LG mobile drivers in the bag of goodies package (second set will pop up a warning for unsigned drivers a few times; hit YES do it anyways, and then re install omap by directing the driver update to the windows drivers folder in the wkparks bootloader1.21 tool. Hopefully this helps.

Here is a much better explaination from drastic00's tutorial. Follow these steps to the T and you should be flashing in no time :)

" A) Uninstall any LG Drivers:

a1) Open Programs and Features through Control Panel

a2)Find any drivers called "LG United Mobile Driver." Right click and select Uninstall, let it work.

a3)Reboot your pc!

B) Be sure you disabled antivirus/Windows Defender, etc. before unpacking these files.

C) Install OMAP4430 by running "OMAPFlashInstaller."

NOTE: if you have Fastboot installed SKIP this step (if you don't know, you don't have it...), but DO link the driver as in f4.

D) Install the two LG Drivers in the “LG United Mobile Drivers” folder: These are “LGUnitedMobileDriver_S497CA20_WHQL_ML_Ver_1. 0” and “LGUnitedMobileDriver_S497MA20_WHQL_ML_Ver_1. 0” The second one will warn it is unsigned, choose to install anyway (you will have to insist on this a few times here).

E)Reboot your pc!

F)Install PC/phone drivers:

f1)Shut down your phone. Remove external sd card, SIM card and battery.

f2) Open Device Manager from Control Panel

f3) Hold volume up on phone and connect to USB port. Keep holding volume up.

f4)Look for "OMAP4430" blinking on and off in Device Manager with a yellow question mark under "Other Devices." (You can let go of the phone). If you do not see it, look for "TI Boards" blinking in device manager and quickly open the arrow. Then uninstall that OMAP4430 (right click, check box to uninstall device and driver, confirm), disconnect phone and reconnect with volume up. Then...

f.4.1) You will need to 'catch' OMAP4430 (with yellow question mark) by right-clicking on it when it appears under "Other Devices." Choose "Update Driver Software."

f.4.2) Pick "Browse my computer for driver software." Then "Let me pick..."

f.4.3) Leave "All..." selected under Devices. Then "Have Disk."

f.4.4) Navigate to the omap4boot-for_optimus-v1.21 folder and choose "omap_winusb" in the usb_drv_windows folder.

f.4.5) Windows will warn the driver is unsigned. Install anyway. An OMAP4430 device should appear under the list of devices. Confirm the selection. Let the driver install.

f.4.6) Disconnect the phone and again reconnect with volume up held.

f5) You should see a popup at the bottom of your screen about drivers (the LG USB drivers) installing. (If you do not see it, disconnect phone, reboot your pc, and again connect it without battery while holding volume up). When you do see drivers installing, let go of the volume button. Click the popup to see the progress. Let it finish.

f6) Look for “LGE CDMA USB SERIAL PORT” in Device Manager. Right click on it and go to Properties

f7) Select the "Port Settings" tab and click 'Advanced'.

f8) Change 'COM Port Number:' to COM41. Click OK, then OK again.

f9) Disconnect your phone from the PC." (From drastic00's noob tutorial)