After a reboot, the displaymodes were STILL there...
And guess what... they work

:-/
dead slow - fillrate issue, dangerously high refreshrate
(85Hz) for that reso, my monitor should NOT be able to
handle that!
I tried the extreme resolutions, and my monitor
managed to show them without any corrupt colors...
I feel like I they can damage my monitor, but as my
hardware can manage it, from the POV of LWJGL the
display-modes are valid. (?)
Something got seriously screwed on my machine, I
don't think this problem should be debugged by LWJGL.