What Hardware version is your router? Look at sticker under router.
What Firmware version is currently loaded? Found on routers web page under status.
What wireless modes are you using? Under Setup/Wireless/Manual.
Try single mode G or mixed G and N?
What security mode are you using? Preferred security is WPA-Personal. WPA2/Auto TPIK and AES. Some WiFi adapters don't support AES, so you might want to try TPIK only.
Any cordless house phones?
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. WMM Enable should be ON however try it OFF. This is QoS for Wireless.