Link>What
Firmware version is currently loaded?
What wireless modes are you using? Under Setup/Wireless/Manual.
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 cordless house phones?
Any other WiFi routers in the area? Link> Use InSSIDer to find out. How many?Ensure the drivers for the LT are up to date?
It's not recommended to Speedtest via Wifi. Too many variables and external conditions can effect accurate results.
Are wired speed tests good?