I've got a QNIX QX2710 monitor, which doesn't work out of the box with X Windows. I was able to get it to work with Fluxbox and Gnome using a custom xorg.conf I found online, but for some reason it doesn't work with KDE.
Under KDE, I'll get the splash screen where the icons light up as parts of KDE load, and the screen is just fine at first. But before it can get to the 2nd icon, my monitor just starts displaying some sort of test pattern. I'm guessing KDE isn't honoring the settings in xorg.conf, but I don't know what I can do about it.
I've attached my current xorg.conf as a file.
Note there's a lot of suggested xorg.conf's floating around for this monitor online, and it took a while for me to find one that worked.
This guy's seemed promising, but it made half of the monitor dim and there were weird visual glitches all over.
FWIW, I'm using Nvidia's 331.67 on a Geforce GTX 670.