xrandr --output LVDS1 --off --output VGA1 --auto 

after login causes Xorg to crash (intermittently)

Alternating the monitor switch between VGA1 and LVDS1 can also cause the crash if it doesn't fail on the first try.

#0  0xffffe430 in __kernel_vsyscall ()
#1  0xb744b7ff in raise () from /lib/libc.so.6
#2  0xb744d140 in abort () from /lib/libc.so.6
#3  0xb7444014 in __assert_fail () from /lib/libc.so.6
#4  0xb72b1d87 in drm_intel_gem_bo_unreference (bo=0x870aaa0) at intel_bufmgr_gem.c:909
#5  0xb72ad714 in drm_intel_bo_unreference (bo=0x870aaa0) at intel_bufmgr.c:80
#6  0xb72727e7 in drmmode_xf86crtc_resize (scrn=0x8271fe8, width=1680, height=1050)
    at drmmode_display.c:1319
#7  0x0817f0f6 in ?? ()
#8  0x081bafd0 in RRScreenSizeSet ()
#9  0x081bb38a in ProcRRSetScreenSize ()
#10 0x080f7160 in ?? ()
#11 0x08088487 in ?? ()
#12 0x08066b85 in _start ()