Optiplex 760 and Omnigear GCS832U KVM

I purchased an Optiplex 760 refurbished with Windows 7 32 bit Professional edition.  The computer works fine with one exception.  I have an Omnigear GCS832U USB 2 port KVM.  It's works with many other Dell desktops, laptops, and Intel Motherboards.  The Omnigear web site specifically states it is compatible with Windows 7.  However the bios of this optiplex will not recognize the keyboard or mouse when the KVM is used.  The Optiplex has the latest BIOS, A15, just upgraded that.  Still, it will not recognize the keyboard or mouse.  The monitor works and works only as long as the keyboard is plugged into the computer.  So there are signals getting from the computer to the KVM.

Has anyone else had this problem?  Has anyone else used 3rd party KVM switches with their Optiplex 760 and had them work?  If so, which maker and model. 

It's baffling to me why this KVM will not be recognized by the BIOS.