I set out to fix this problem one morning after installing Win 7 64 bit. I found what chipsets the WLI-U2-G300N used.
http://www.wikidevi.com/wiki/Buffalo_WLI-U2-G300N
The Marvell 88W8362 is the MAC controller.
The Marvell 88W8060 is the RF controller.
Now, take a look at this:
http://www.wikidevi.com/wiki/TRENDnet_TEW-624UB_rev_A1
The TRENDnet TEW-624UB rev A1 uses the exact same ICs (Integrated Chips). A quick search for TEW-624UB A1 took me to their website to download drivers.
http://www.trendnet.com/downloads/list_subcategory.asp?SUBTYPE_ID=1082
I downloaded the zip attached to the driver link.
Then I had to use WinRAR to open the file as it doesn't open correctly. (7-zip might recognize and open it, I don't know for sure)
I copied the files in the zip file to my hard drive.
Then I went into my device manager to install the driver manually.
***Look online for manually installing drivers in Win 7 if you don't know how.***
I pointed it to the Vistax64 folder, and let it start the driver install.
HERE is where I ran into something strange. I let it run for a few minutes while continuing to do research on the Marvell chipsets. It didn't look like finished (blue bar still going across the screen over and over), so I clicked the X in the top right to stop it. When I looked at my Device Manager, it showed: TRENDnet TEW-624UB 300Mbps Wireless N USB 2.0 Adapter
I had to manually setup my wireless network with my WPA2 encryption, and VIOLA!!!! I was working! I disconnected the LAN cable and downloaded Passmark's Wireless Mon software to verify everything. The transfer speed was over 3 Mb. That's 3 MegaBITS, not megabytes.... per second. I've got a 10Mb line, so that's not too bad. Likely the site I was downloading it from didn't give me a 10Mb download speed, so it's looking pretty good. WirelessMon showed the following info.
Strength -46 dBm 57%
Speed (Mbits)148
The max on the Netgear WNR834B I'm running is 270 Mbps. Clearly I still have a little work to do between the router and the wireless adapter, but it's a really good start. Likely it's an issue with either MIMO, or not using both antenas. Oh, that's another point. The Buffalo WLI-U2-G300N only uses two of the antenas. One is just a plastic stump. Still, I think I can get a higher connection speed if I get the MIMO working correctly in a 2x2 antena configuration. Will try streaming HD after I tweak everything.
FYI, the Windows built in service (Wireless Zero Configuration I think it's called) will not always correctly identify the link speed. Mine went back and forth between 1Mb and 270Mb.
Hope this helps everyone!