Found your answer, I think. Apparently one of the links has the 32 bit and 64 bit backwords.
http://forums.logitech.com/t5/G-series-Gaming-Mice/Windows-64-bit-LGS-Software-Incorrectly-Linked-at-Logitech/td-p/1345228
Got one from WM on sale and love it. the LED's are very bright. I use electrical tape to cover the LED lights, and the light still comes from the air openings on the front edges, but that's a good thing to see if everything is still working.
I apologize, I used the model number, not the link. Obviously, they don't price match, except when they do!..
http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=WDBAAU0020HBK-NESN+price+match&rh=i%3Aaps%2Ck%3AWDBAAU0020HBK-NESN+price+match
edit: but now the price JUST...
Amazon price $96.99
Amazon quote:
"Pricing
We offer you consistently low prices on every item in our store. With the exception of Televisions, we do not price match with other retailers. We do not have bulk order discounts."