Check the drivers for usb are ok in device manager, check if the port is actually working fine by connecting a pen drive. Also please try with other usb ports on the back side of the computer which are directly connected to the motherboard.
I've just recently purchased a Microsoft Ergonomic Keyboard 4000, and I seem to have a problem or two with it. Since I've connected it to my PC (via USB port), the performance has drastically fell, and loading times have increased to 4 times of the normal. I assume it has something to do with my new keyboard, but I have found no solutions so far (when starting up windows with a regular PS/2 keyboard connected, it seems everything turns back to normal). Could you guys help me out?
Basic System Information
OS: WinXP with SP3
CPU: AMD Athlon(tm) 64 X2 Dual Core Processor 5600+