Are you on Windows 7?
I would more than video like to see a screen shot of the drivers in your pc Device Manager (when phone is connected to pc by usb, you hold volume up on phone when you plug it in).
There should be 'omap 4430' in 'other devices' in pc Device Manager. If correctly installed, it should NOT be flashing/blinking on and off. You must use the driver from the wkpark Fastboot package, not the one from the 'omap4flash installer' pack.
There are also two LG drivers that must be installed to pc. And there should be LG Cosmo device appearing in Device Manager someplace also, port set to 41.
I ask because driver install can be tricky or difficult, and confusing when you first do all of that. And, it is very important to have it all correct to flash successfully. Usually it is the problem when flash will not complete or start.
It also adds to difficulty that you must translate the instructions...