Monitor positions swap spontaneously

I am running CentOS 6.5 on a system with a GeForce GTX 750 graphics card. One of my monitors is a Seiki/4K 38" monitor and the second is a Dell 30" monitor. I've configured the Seiki as the leftmost (primary) monitor, and the Dell as the right-hand monitor. Everything works fine except that periodically, usually once or twice a day, the monitor positions swap, with the Dell suddenly becoming the left-hand monitor and the Seiki becoming the right-hand monitor. This causes windows to get moved around and generally messing things up. I have to launch the NVidia control panel and move the Dell back to the right and hit "Apply". This usually corrects the problem, although sometimes it doesn't work and I have to do the Apply a second time. Once it works, my application windows are back in their original positions as if nothing had happened.

I have no idea what's causing this. Does anyone have any suggestions what might be wrong?

Check the xorg log in /var/log to see if there is a clue

That did indeed show some curious information. I waited for the switch to occur again and immediately checked the log file. Unfortunately I'm not an xorg guy and don't quite know what it implies, or even if the messages imply anything. I have a similar setup on my work PC, with a 4K Seiki monitor as my middle (primary) monitor bordered by two 1920x1200 monitor monitors on each side (in portrait mode). That orientation works great, although I'm using an older NVidia graphics card (GeForce 640 GT). Do these messages mean anything specific? Note that I have to run the Seiki at 30Hz to get the full 3840x2160 resolution. Everything seems to be working fine other than this periodic swap (which is getting more annoying everyday). I've attached my 10.monitor.conf file (renamed to xord.txt) if a xorg expert wants to take a look. I put this together with some help from a Google search discussing how to support the Seiki monitor.

[551668.561] (**) NVIDIA(0): Using HorizSync/VertRefresh ranges from the EDID for display
[551668.561] (**) NVIDIA(0): device SEK SE39UY04 (DFP-2) (Using EDID frequencies has
[551668.561] (**) NVIDIA(0): been enabled on all display devices.)
[551668.561] (WW) NVIDIA(GPU-0): Unrecognized ModeValidation token "AllowNon60hzmodesDFPModes";
[551668.561] (WW) NVIDIA(GPU-0): ignoring.
[551668.561] (WW) NVIDIA(GPU-0): Unrecognized ModeValidation token "NoEDIDDFPMaxSizeCheck";
[551668.561] (WW) NVIDIA(GPU-0): ignoring.
[551668.561] (WW) NVIDIA(GPU-0): Unrecognized ModeValidation token
[551668.561] (WW) NVIDIA(GPU-0): "NoDFPNativeResolutionCheck"; ignoring.
[551668.561] (II) NVIDIA(GPU-0): Mode Validation Overrides for SEK SE39UY04 (DFP-2):
[551668.561] (II) NVIDIA(GPU-0): NoMaxPClkCheck
[551668.561] (II) NVIDIA(GPU-0): NoEdidMaxPClkCheck
[551668.561] (II) NVIDIA(GPU-0): NoMaxSizeCheck
[551668.561] (II) NVIDIA(GPU-0): NoHorizSyncCheck
[551668.561] (II) NVIDIA(GPU-0): NoVertRefreshCheck
[551668.561] (II) NVIDIA(GPU-0): AllowNonEdidModes
[551668.589] AUDIT: Sat Aug 23 20:17:48 2014: 2312: client 51 connected from local host ( uid=0 gid=0 pid=2702 )
Auth name: MIT-MAGIC-COOKIE-1 ID: 565
[551668.593] AUDIT: Sat Aug 23 20:17:48 2014: 2312: client 51 disconnected
[551668.938] (II) NVIDIA(GPU-0): Display (DELL 3007WFP (DFP-0)) does not support NVIDIA 3D
[551668.938] (II) NVIDIA(GPU-0): Vision stereo.
[551668.948] (II) NVIDIA(GPU-0): Display (SEK SE39UY04 (DFP-2)) does not support NVIDIA 3D
[551668.948] (II) NVIDIA(GPU-0): Vision stereo.
[551669.047] (II) NVIDIA(0): Setting mode "HDMI-0: nvidia-auto-select @3840x2160 +2560+0 {ViewPortIn=3840x2160, ViewPortOut=3840x2160+0+0}"
[551669.164] (II) NVIDIA(0): Setting mode "DVI-I-1: nvidia-auto-select @2560x1600 +0+0 {ViewPortIn=2560x1600, ViewPortOut=2560x1600+0+0}, HDMI-0: nvidia-auto-select @3840x2160 +2560+0 {ViewPortIn=3840x2160, ViewPortOut=3840x2160+0+0}"
[551669.522] AUDIT: Sat Aug 23 20:17:48 2014: 2312: client 48 connected from local host ( uid=0 gid=0 pid=2702 )
Auth name: MIT-MAGIC-COOKIE-1 ID: 565
[551669.573] AUDIT: Sat Aug 23 20:17:49 2014: 2312: client 48 disconnected
[551672.498] (II) NVIDIA(0): Setting mode "DPY-1:nvidia-auto-select@2560x1600+0+0{ViewPortIn=2560x1600,ViewPortOut=2560x1600+0+0},DPY-3:nvidia-auto-select@3840x2160+2560+0{ViewPortIn=3840x2160,ViewPortOut=3840x2160+0+0}"
[551674.882] (II) NVIDIA(0): Setting mode "DPY-1:nvidia-auto-select+3840+0,DPY-3:nvidia-auto-select+0+0{viewportout=3840x2160+0+0}"
[551675.024] AUDIT: Sat Aug 23 20:17:54 2014: 2312: client 51 connected from local host ( uid=0 gid=0 pid=2702 )
Auth name: MIT-MAGIC-COOKIE-1 ID: 565