I installed the drivers from the website before I got the card and when I inserted the card it worked fine on vista 64 with the O2 router.
Edit: After using it for 2 days, it started to cause my computer to freeze when I start playing online games. Googled the problem, found many with the same problem...
It seems that the drivers on the edimax website arent really suitable for vista 64 either.
I've installed the Ralink drivers instead found on the ralink website (you need the RT2860 drivers for this card)
Hopefully its fixed now, but I will test for a few days first and report my findings :p