Try single mode G or mixed G and N on 2.4Ghz.
Channel Width set for Auto 20/40Mhz or try
20Mhz only.
Try setting a manual channel to a open or unused channel. 1, 6 or 11. 11 for single mode N if the channel is clear.
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? Link> Use
InSSIDer to find out. How many?
Turn off WISH, and WPS under Advanced.
Try turning off Short GI, WLAN Partition,and Extra Wireless Protection if you have it. Under Advanced/Advanced Wireless.
Enable
WMM Enable Under Advanced/Advanced Wireless
Let us know if this helps.