@ webbusiness23.. I just bought this phone today & had the same problem. In addition to the above note on turning on usb debugging i also did the below steps & finally got it to work! All my files are now being copied as i am typing this reply...
1. Downloaded & installed the 'LG Mobile phone updater' (though not sure why its called that way)
2. Installed the USB driver --- The app only has US as the option for country & so when you hit to install USB driver you are required to choose by operator & they are obviously all US providers & none of them have this model showing up too! So installed for some model which says PXXX in the name
3. Reconnect the phone - Message in the top line about US debugging mode
4. Pull it down & chose 'Turn on USB mass storage' and you are good to go
at 12 AM on a saturday i have created a new account on this forum & posted just to be able to help you (coz i knw how irritating it would be to not be able to connect on USB), so please do revert if this worked or if you had already figured out the solution.