I actually have the exact same problem, and managed to partially solve it by downloading the Vista x64 drivers for the Marvell chipset used in the WG311v3.
First be sure to remove the crappy Netgear software you might have tried to install in the first place.
You then need to locate the drivers (MRVW13C.sys for me) and the inf you need in the Marvell package, and then point the "Add new hardware" wizard to the folder you placed the driver in. Not sure I'm clear there.
But the issue is that the driver is not signed by Microsoft, so you'll have to enable the "Test Mode" to allow the driver to load when windows start. See there for how to do that : Driver Signature Enforcement Overrider 1.3b - NGOHQ.com
I had it working so far, pretty well, except for the "Test Mode" in the bottom right of my screen.
But recently I Had to reinstall Windows 7, and I saw in the optional updates proposed by Windows Update a "Marvell Driver for Netgear WG311v3" (note this is the Marvell driver, not the Netgear one), so I was like "Yay, problem solved", EXCEPT this is the exact same driver I spoke about above, so it won't load either. Personally, I would expect a driver proposed by Windows Update to work, or at least LOAD, but apparently that's too much to ask. Isn't there a way to have this driver signed once and for all?