It seems like the adaptor only has XP drivers on Linksys' site, which probably means it has 32-bit drivers only. Which is probably why it worked with Vista that was likely 32-bit, but doesn't work with Win7 64-bit.
Time for a new wireless adaptor.
Edit:
http://www.newegg.com/Product/Produc...82E16833127076
That is only $8 shipped, and has 64-bit drivers.