It's funny because here's the thing: I've had the Env2 for over a year now. When I first got it all my computers had XP, and connected up just fine, no problems. Then I got a newer computer that runs on Vista. I had incorrectly, I guess, assumed that Vista would make life easier, (

) after all isn't that what new technology is for. So when I first connected my phone to my vista computer it said updating drivers and I thought "sweet, it's going to just install it for me." But it didn't. I thought, OK no problem I'll just download the USB drivers and connect my phone.
And. So. I downloaded the drivers. After a good hour of finagling, arguing with my phone and giving it some polite encouragement ("You can do this phone, don't quit on me now, we're so close") i finally did get it to connect. Like the OP, once, just the initial time.
Every time since then I have connected it, it's said that it needs the drivers. So finally I just gave up and, since the only reason I was even connecting to it in the first place was to get media sync'd to my phone I've just been using the jumpdrive adapter that came with the sd card. Or would have until last night I couldn't find my adapter and had to once again try to wrestle with my vista computer to see if it could get some files on there.
After installing and reinstalling the drivers, I got bupkis. And finally, figured out that I don't need my jumpdrive adapter as long as I have my USB cord and can connect via menu>settings>tools>usb mass storage (it works almost exactly the same as having it plugged in with a jumpdrive adapter.
If you can, un-install the driver from your computer, then download it from here:
http://www.imjosh.com/LG_USB_Driver.zip then install it, when doing all this, don't have your phone connected to your PC.
I followed these steps exactly (uninstalled old drivers and then downloaded and attempted to install those drivers) and it gives me this exact error message: "The version of the operating system installed does not support USB modem drivers. Please upgrade your operating system to Windows 98 SE or later."
Oh LOL.