I missed the number of computers you need a KVM for...
BUT www.compusa.com offers a 2 port KVM for under $30.00
http://www.compusa.com/products/product_info.asp?product_code=50315780&pfp=cat3
Hope this helps!
I think a couple of you have hit around it and this may not be it. But Phosphor, like used on CRT screens looses it brightness over time. The harder you drive it the quicker it looses its brightness... I think you may need to pulse modulate the LEDs instead of leaving them STEADY ON!