I tried three different versions of LG's USB drivers before I found one that worked for me. I'm not at home, so I can't send them to you. But just PM me and when I'm home in the morning I can send you the one that worked for me.
Also, are you sure you're putting your phone in the correct USB debugging mode? As I recall, it needs to be in "Internet" mode.
Sent from my LG Spectrum using Tapatalk