Kind of hard to have your problem solved in under an hour... give the guys some time.
Question... can you hardwire into the router? If so, what are the speeds then? If you have one of the latest motherboards, I am sure it has on-board LAN connection. If you do this test, make sure to disconnect and pull out the wireless card.
I am personally using a 2 year old Linksys wireless card I had laying around (not even Win 7 "certified") and it runs perfectly.