Signal 11 in xorg-server

[Руслан Бондарь]

Hello all.
Sometimes my xorg server crashes.
Xorg-server version: 1.5.2
Linux distro: gentoo
X11 wm: openbox-3.4.7.2

I notice this problem only when I'm using dual-screen configuration.
I have dual headed nVidia GeForce 8600 with proprietary driver.
The piece of configuration for videocard follows.
If you need some additional information. Or some experiments - welcome. I can repeat the issue at any time.
I'm not sure, the videocard is the root case of the problem, because a little earlier I had similar problem with my hotkeys, which are formed as additional synaptics touchpad, but uses evdev driver instead of synaptics.

Thanks for any suggestions.

The piece of the log.
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Backtrace:
0: /usr/bin/X(xf86SigHandler+0x7a) [0x80c8836]
1: [0xffffe400]
2: /usr/bin/X(Dispatch+0x33d) [0x808a67a]
3: /usr/bin/X(main+0x46f) [0x80719b5]
4: /lib/libc.so.6(__libc_start_main+0xe0) [0xb7c1f630]
5: /usr/bin/X [0x8070dd1]

Fatal server error:
Caught signal 11.  Server aborting
############################

The piece of the config:
############################
Section "ServerLayout"
        Identifier     "X.org Configured"
        Screen         0 "Screen0" 0 0
        Screen         1 "Screen1" RightOf "Screen0"
        InputDevice    "Mouse0" "CorePointer"
        InputDevice    "Synaptics" "SendCoreEvents"
        InputDevice    "Keyboard0" "CoreKeyboard"
        InputDevice    "Multimedia" "SendCoreEvents"
EndSection

Section "Device"
        Identifier  "nvout1"
        Driver      "nvidia"
        VendorName  "nVidia Corporation"
        BoardName   "GeForce 8600M GT"
        BusID       "PCI:1:0:0"
        Option      "RenderAccel" "true"
        Option      "AddARGBGLXVisuals" "true"
        Option      "AllowGLXWithComposite" "true"
        Option      "DisableGLXRootClipping" "true"
        Option      "HWcursor"
        Option      "RandRRotation" "on"
        Option      "BackingStore" "on"
        Option      "NoFlip" "true"
        Screen      0
EndSection
############################