Please explain X strangeness

[Mark Neidorff <mark@neidorff.com>]

Hi all,

Debian Lenny system patched up using nvidia driver.  I have a KVM switch 
because I am setting up a new machine.  Normal behavior is that X starts just 
fine  if the Debian box has KVM "focus" as it boots.  If it doesn't have 
"focus" (I see the video from the other computer on the screen) the I get an 
"out of range" error on the screen.  A quick ctrl-alt-backspace restarts the 
X server and everything is fine.  Recently, I've gotten a 3rd PC to setup.  
Since my monitor has multiple video inputs, I hooked the 3rd PC to video2 on 
the monitor.  Yesterday, I unhooked the 3rd PC from the monitor (but left the 
cable hooked to the monitor with an unattached end).  Today when I tried to 
start X, even when I see the output of the debian box on the monitor, I got 
an "out of range" error.  Tapping ctrl-alt-backspace restarts X, but does not 
allow X to start.  Here is the part I would like an explanation for....I 
pulled the video cable (that is attached to nothing) off of the connector on 
the monitor, tapped ctrl-alt-backspace, and X started just fine.  Why does 
the presence of a disconnected cable give X a problem?

Thanks for any insight.

Mark