Hi,
this has happened more than once now: when I removed the external monitor DVI cable, the X server has crashed. I eventually managed to recover, here is what was in the logs:
[ 28038.041] (II) NVIDIA(GPU-0): Display (Samsung SMXL2370HD (DFP-2)) does not support NVIDIA
[ 28038.041] (II) NVIDIA(GPU-0): 3D Vision stereo.
[ 28038.041] () NVIDIA(0): Using HorizSync/VertRefresh ranges from the EDID for display
[ 28038.041] ( ) NVIDIA(0): device Samsung SMXL2370HD (DFP-2) (Using EDID frequencies
[ 28038.041] (**) NVIDIA(0): has been enabled on all display devices.)
[ 28039.350] (II) NVIDIA(0): Setting mode "LVDS-0: nvidia-auto-select @1920x1080 +0+0, DVI-I-1: nvidia-auto-select @1920x1080 +0+0"
[ 28040.918] (II) NVIDIA(0): Setting mode "LVDS-0: nvidia-auto-select @1920x1080 +1920+0, DVI-I-1: nvidia-auto-select @1920x1080 +0+0"
[ 34292.155] (II) NVIDIA(0): Setting mode "NULL"
[ 34292.191] (II) NVIDIA(0): Setting mode "NULL"
[ 34292.266] (II) NVIDIA(0): Setting mode "LVDS-0: nvidia-auto-select @1920x1080 +0+0"
[ 34297.890] nvLock: client timed out, taking the lock
[ 34300.946] (WW) NVIDIA(0): WAIT (2, 6, 0x8000, 0x0000fff0, 0x00000004)
[ 34304.477] (WW) NVIDIA(0): WAIT (0, 6, 0x8000, 0x00000004, 0x00000004)
[ 34385.177] (WW) NVIDIA(0): WAIT (2, 6, 0x8000, 0x00009ce0, 0x00009ec0)
[ 34389.653] (WW) NVIDIA(0): WAIT (0, 6, 0x8000, 0x00009ec0, 0x00009ec0)
(EE) [mi] EQ overflowing. Additional events will be discarded until existing events are processed.
(EE)
(EE) Backtrace:
(EE) 0: /usr/bin/Xorg (xorg_backtrace+0x36) [0x46c466]
(EE) 1: /usr/bin/Xorg (mieqEnqueue+0x26b) [0x581d6b]
(EE) 2: /usr/bin/Xorg (0x400000+0x4de02) [0x44de02]
(EE) 3: /usr/lib64/xorg/modules/input/evdev_drv.so (0x7fc455d52000+0x64b4) [0x7fc455d584b4]
(EE) 4: /usr/bin/Xorg (0x400000+0x89717) [0x489717]
(EE) 5: /usr/bin/Xorg (0x400000+0xb2e88) [0x4b2e88]
(EE) 6: /lib64/libpthread.so.0 (0x3262c00000+0xf000) [0x3262c0f000]
(EE) 7: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7fc45692d000+0x8f53d) [0x7fc4569bc53d]
(EE) 8: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7fc45692d000+0x90dc5) [0x7fc4569bddc5]
(EE) 9: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7fc45692d000+0x114afe) [0x7fc456a41afe]
(EE) 10: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7fc45692d000+0x7b578) [0x7fc4569a8578]
(EE) 11: /usr/bin/Xorg (0x400000+0xcff04) [0x4cff04]
(EE) 12: /usr/bin/Xorg (0x400000+0xce8e4) [0x4ce8e4]
(EE) 13: /usr/bin/Xorg (miPointerUpdateSprite+0x29a) [0x58c10a]
(EE) 14: /usr/bin/Xorg (0x400000+0x18c3bd) [0x58c3bd]
(EE) 15: /usr/bin/Xorg (0x400000+0xdc8fb) [0x4dc8fb]
(EE) 16: /usr/bin/Xorg (0x400000+0x126647) [0x526647]
(EE) 17: /usr/bin/Xorg (0x400000+0x41ba9) [0x441ba9]
(EE) 18: /usr/bin/Xorg (WindowHasNewCursor+0x37) [0x442f77]
(EE) 19: /usr/bin/Xorg (ChangeWindowAttributes+0xba5) [0x467ba5]
(EE) 20: /usr/bin/Xorg (0x400000+0x33a8d) [0x433a8d]
(EE) 21: /usr/bin/Xorg (0x400000+0x3965a) [0x43965a]
(EE) 22: /usr/bin/Xorg (0x400000+0x280ca) [0x4280ca]
(EE) 23: /lib64/libc.so.6 (__libc_start_main+0xf5) [0x3262421a05]
(EE) 24: /usr/bin/Xorg (0x400000+0x28411) [0x428411]
(EE)
(EE) [mi] These backtraces from mieqEnqueue may point to a culprit higher up the stack.
(EE) [mi] mieq is NOT the cause. It is a victim.
[ 34424.735] [mi] Increasing EQ size to 1024 to prevent dropped events.
[ 34424.736] [mi] EQ processing has resumed after 43 dropped events.
[ 34424.736] [mi] This may be caused my a misbehaving driver monopolizing the server’s resources.
[ 34606.761] (II) NVIDIA(0): Setting mode "LVDS-0: nvidia-auto-select @1920x1080 +0+0"
P.S.
You might want to allow uploading tar.gz files, this is what nvidia-bug-report.sh produces by default.