Force video mode without EDID information

I've checked your original xorg.conf setting, and found there are some suspicious items:

1. Have you Had checked that your HorizSync and VertRefresh settings were correct?
2. ÌgnoreEDID was deprecated, just use UseEDID
3. Remove "NoVesaModes,NoXServerModes", just use Option "ModeValidation" "NoEDIDModes"
4. Instead of using Option "MetaModes" "1920x1080_new", use Option "MetaModes" "1920x1080 +0+0"

I also found this option in nvidia's user manual:

Appendix B. X Config Options http://us.download.nvidia.com/XFree86/Linux-x86_64/384.69/README/xconfigoptions.html

"AllowNonEdidModes": if a mode is not listed in a display device's EDID mode list, then the NVIDIA X driver will discard the mode if the EDID 1.3 "GTF Supported" flag is unset, if the EDID 1.4 "Continuous Frequency" flag is unset, or if the display device is connected to the GPU by a digital protocol (e.g., DVI, DP, etc). This token disables these checks for non-EDID modes.

May it be helpful.

As it turns out, this might be a bug after all. My X server ignores every configuration made in the standard xorg.conf. Instead, it only accepts configuration in the /usr/share/X11/xorg.conf.d/*.conf files, but only in the files already present. Therefore I hijacked one of the already existing configuration files. I know that an update will eventually overwrite them at some point in the future. To solve the initial issue, I used a custom modeline:

Section "Screen"
    Identifier "My Screen"
    Device "My Card"
    Monitor "SL23T-1 LED"
    Option "RegistryDwords" "EnableBrightnessControl=1"
    Option "UseEdid" "False"
    Option "CustomEdid" "CRT-1:/etc/X11/nvidia_edid.bin"
    Option "ExactModeTimingsDVI" "True"
    Option "ModeDebug" "True"
    DefaultDepth    24
    SubSection     "Display"
               Depth       24
               Modes      "1920x1080"
    EndSubSection

EndSection

Section "Device"
    Identifier "My Card"
    Driver "nvidia"
    Option "NoLogo" "True"
EndSection

Section "Monitor"
    Identifier "SL23T-1 LED"
    VendorName "FUS"
    ModelName "SL23T-1 LED"
    # Block type: 2:0 3:fd
    HorizSync 67.5 - 67.5
    VertRefresh 60.0

    ModeLine "1920x1080" 148.50 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync
    Option   "DPMS"

EndSection

What i did (on 14.04) after pulling my hair out over this (Google shows a LOT of hits about older versions of Ubuntu, but nothing about newer ones) was ignore the Xorg.conf stuff altogether. Instead, i enabled automatic logon, and put the following in my .xprofile:

xrandr --fb 1920x1080
xrandr --newmode "1920x1080_59.9" 138.5 1920 1968 2000 2080 1080 1083 1088 1111 +HSync -VSync
xrandr --addmode VGA1 "1920x1080_59.9"
xrandr --output VGA1 --mode 1920x1080_59.9

I got the parameters of newmode by using cvt -r 1920 1080. If you have a chance to turn on DDC for a while (for example, your KVM switch doesn't handle DDC, but you can plug the monitor directly into the video card to debug), you can use xrandr --verbose -q as well.