Is that you unplug the ASUS device from where it is plugged in and move it to a high speed USB port (2.0). If you have a HUB installed, it is not USB 2.0. If you are plugged into a motherboard port then your motherboard port is not operating at the 2.0 speed.
I'm using ASUS A9RP series just bought months ago and I'm using Windows XP SP2. Everytime when i switch on my computer, a message will pop up and shows HI-SPEED USB Device Attached To non-HI-SPEED Hub. The message box also shows recommendation for this problem. It shows "Disconnect the ASUS USB Wireless Network Adapter from its current port and then connect it to the one of the ports on a hub shown in bold type (USB Root Hub)." How can i disconnect the adapter from it's current port?