When the monitor say input not recoqnized. I have same problem when I played
with LTSP last year, one monitor can't display Xwindow, only blank black
screen.
Another solution is boot with livecd (any live cd is OK, I use backtrack)
and write down modeline string from xvidtune then apply it to your xorg.conf.
I use this trick to solve my LTSP display problem.
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