Dan
When you are using multiple wireless hardware devices and they are in close proximity, you need to configure the devices to use different channels to transmit and receive their commands.
I don't use these particular devices, but I'm sure you will find the instructions for configuring the transmission or receiving channels in the documentation that came with the keyboards or the help file for the software that came with the devices.
Microsoft Hardware Mouse and Keyboard – Home Page:
http://www.microsoft.com/hardware/mouseandkeyboard/default.mspx
Hope this helps.
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Ronnie Vernon
Microsoft MVP
Windows Desktop Experience
