Check the wireless mode isn't set to B only, if you have the 2701HG-B. Check/change your wireless security settings, make sure you're using WPA2-PSK (personal mode) if available, use AES encryption if possible, but if it still doesn't work try TKIP. If you have the wireless channel set to auto, try changing it to 1, 6, or 11.
It's best to stick with the same chipset manufacturer on all devices to achieve the best compatibility and performance. (my router has an AR9580 so all my WLAN NICs have Atheros radios.)