Try single mode G or mixed G and N on 2.4Ghz and single mode N on 5Ghz?
Channel Width set for Auto 20/40Mhz or try 20Mhz only.
Try setting a manual channel to a open or unused channel.
What security mode are you using? Preferred security is WPA-Personal. WPA2/AES Only. Some WiFi adapters don't support AES, so you might want to try TPIK only or Auto.
Any other WiFi routers in the area? Use InSSIDer to find out.Turn off Short GI, WLAN Partition and Extra Wireless Protection if you have it. Under Advanced/Advanced Wireless.