According to the manual, I should connect the USB connection to my computer and "USB Connected" should appear in the notifications. When I do this, I don't see the notification and it doesn't show up on my computer.
It looks like there have been some issues with SD cards- mine is one that I took out of my old phone. Maybe 1.5 years old. I can use the music that was on it and I think I have successfully exported my contacts to it so it appears to at least be working somewhat ok.
I had the same problem, and it frustrated me for a few minutes as well.
You have to go to the LG website (www.lg.com), search for the Optimus to find the product page there (it's the LS670), click the Resources tab, then under the Downloads it will say 'LG Android driver'. Download and instal that, then connect the phone and it will read it.
Hope that helps!
Specific USB drivers should not be required for any phone made within the last 2 years for connections like that. The default Windows drivers work perfectly for the phones, unless you don't have an Internet connection and it can't download them automatically for you.
In most cases Android phones not being able to connect to the computer is caused by the debugging mode being turned on. You can check this setting by going to Settings > Applications > Development. All of the boxes in there should be turned off unless you know you need them on. If you don't know if you need them, you don't.