Maybe you have already determined that ndiswrapper is your best option, but just in case you haven't: the Netgear WG511T is known to work very well with the madwifi driver, as long as your card has the Atheros chipset. I happen to own the same model myself and it works great, check out the project homepage
for more info.
But if you're unlucky and the chipset in your card is not supported by madwifi (or any other project), then you could try ndiswrapper.
I hope that helps.