I had a problem, I had flashed the wrong recovery on my phone, that of the lg optimus 2x, and it had bricked my phone and I was stuck with a paperweight, but then I learned of the S/W button combination-- hold volume up, E on the keyboard and the power button. the phone booted into software upgrade mode, and with this utility I was able to flash a stock rom back into the phone, which also replaced the incorrect recovery.
The only thing that has to be changed is that you need to use the CS_EMERGENCY mode instead of DIAG, or else it won't work.
so if you ever find yourself in that situation, grab your carrier's stock rom and do what I did. I have a working phone after over two months of not being able to use it thanks to that.