I think it's an hardware problem, but to be sure, I suggest you to test your router in another place (friend, parent, etc.) with another client machine...

Did you try to upgrade/downgrade the firmware? If yes, you have probably to replace your router...

A laptop has a powerful internal antenna so it is able to get a good connection. Nevertheless, your card has probably a malfunction requiring a RMA if it doesn't work better with the last...

Wireless adaptors are very sensible to antennas positions or malfunctions...

I suggest you to check near the router. Check also all the antennas.

Hi, There is a lot of signals around creating interferences. Try to force the bandwidth to 20Mhz...