I'm using the current NVIDIA driver 346.35 on an Arch Linux system with a large display (3200x1800). When I add a second display (1920x1200) left of the main display and try to move a KDE panel to the second display, Xorg sometimes crashes with segmentation fault.

Xorg.0.log:

[ 42727.985] (II) NVIDIA(0): Setting mode "DP-4: nvidia-auto-select @3200x1800 +1920+0 {ViewPortIn=3200x1800, ViewPortOut=3200x1800+0+0}"
[ 42729.345] (II) NVIDIA(0): Setting mode "DP-4: nvidia-auto-select @3200x1800 +1920+0 {ViewPortIn=3200x1800, ViewPortOut=3200x1800+0+0}, DP-5: nvidia-auto-select @1920x1200 +0+0 {ViewPortIn=1920x1200, ViewPortOut=
1920x1200+0+0}"
[ 42743.104] (EE) 
[ 42743.104] (EE) Backtrace:
[ 42743.108] (EE) 0: /usr/lib/xorg-server/Xorg (xorg_backtrace+0x56) [0x590416]
[ 42743.108] (EE) 1: /usr/lib/xorg-server/Xorg (0x400000+0x194579) [0x594579]
[ 42743.108] (EE) 2: /usr/lib/libc.so.6 (0x7fb0f3df6000+0x33540) [0x7fb0f3e29540]
[ 42743.108] (EE) 3: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fb0ecef0000+0xb7ef2) [0x7fb0ecfa7ef2]
[ 42743.108] (EE) 4: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fb0ecef0000+0xc292f) [0x7fb0ecfb292f]
[ 42743.108] (EE) 5: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fb0ecef0000+0x5d92f3) [0x7fb0ed4c92f3]
[ 42743.108] (EE) 6: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fb0ecef0000+0x5d9ac5) [0x7fb0ed4c9ac5]
[ 42743.108] (EE) 7: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fb0ecef0000+0x5d9c6d) [0x7fb0ed4c9c6d]
[ 42743.108] (EE) 8: /usr/lib/xorg-server/Xorg (0x400000+0x11c031) [0x51c031]
[ 42743.108] (EE) 9: /usr/lib/xorg-server/Xorg (0x400000+0xc93a2) [0x4c93a2]
[ 42743.108] (EE) 10: /usr/lib/xorg-server/Xorg (0x400000+0xca68f) [0x4ca68f]
[ 42743.108] (EE) 11: /usr/lib/xorg-server/Xorg (0x400000+0xc79f2) [0x4c79f2]
[ 42743.108] (EE) 12: /usr/lib/xorg-server/Xorg (0x400000+0x113772) [0x513772]
[ 42743.108] (EE) 13: /usr/lib/xorg-server/Xorg (ConfigureWindow+0x45f) [0x46434f]
[ 42743.108] (EE) 14: /usr/lib/xorg-server/Xorg (0x400000+0x32fc8) [0x432fc8]
[ 42743.108] (EE) 15: /usr/lib/xorg-server/Xorg (0x400000+0x38807) [0x438807]
[ 42743.108] (EE) 16: /usr/lib/xorg-server/Xorg (0x400000+0x3c97b) [0x43c97b]
[ 42743.108] (EE) 17: /usr/lib/libc.so.6 (__libc_start_main+0xf0) [0x7fb0f3e16800]
[ 42743.108] (EE) 18: /usr/lib/xorg-server/Xorg (_start+0x29) [0x426e29]
[ 42743.108] (EE) 
[ 42743.108] (EE) Segmentation fault at address 0x0
[ 42743.108] (EE) 
Fatal server error:
[ 42743.108] (EE) Caught signal 11 (Segmentation fault). Server aborting
[ 42743.108] (EE) 
[ 42743.108] (EE) 
Please consult the The X.Org Foundation support 
         at http://wiki.x.org
 for help. 
[ 42743.108] (EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information.
[ 42743.108] (EE) 
[ 42744.347] (EE) Server terminated with error (1). Closing log file.