this command kills my Xserver:-(

    # xrandr  --output LVDS1 --mode 1024x768

it's a valid resolution:

# xrandr 
Screen 0: minimum 320 x 200, current 1280 x 800, maximum 32767 x 32767
LVDS1 connected 1280x800+0+0 (normal left inverted right x axis y axis) 261mm x 163mm
   1280x800       60.0*+   50.0  
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
VGA1 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
DP1 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)


from Xorg.0.log.old:

[...]
[ 80098.748] setversion 1.4 failed
[ 80143.868] (II) intel(0): resizing framebuffer to 1024x768
[ 80143.877] (II) intel(0): switch to mode 1024x768@60.0 on pipe 0 using LVDS1, position (0, 0), rotation normal
[ 80144.168] (EE) 
[ 80144.168] (EE) Backtrace:
[ 80144.168] (EE) 0: /usr/bin/X (xorg_backtrace+0x3d) [0x585acd]
[ 80144.168] (EE) 1: /usr/bin/X (0x400000+0x189839) [0x589839]
[ 80144.168] (EE) 2: /lib64/libpthread.so.0 (0x7f845e00a000+0xf9f0) [0x7f845e0199f0]
[ 80144.168] (EE) 3: /lib64/libc.so.6 (__vsprintf_chk+0x54) [0x7f845cf51d84]
[ 80144.168] (EE) 4: /lib64/libc.so.6 (__sprintf_chk+0x7d) [0x7f845cf51d0d]
[ 80144.168] (EE) 5: /usr/lib64/xorg/modules/drivers/intel_drv.so (0x7f8458e53000+0x5dcc2) [0x7f8458eb0cc2]
[ 80144.168] (EE) 6: /usr/bin/X (xf86ProbeOutputModes+0x1db) [0x4afebb]
[ 80144.168] (EE) 7: /usr/bin/X (0x400000+0xb92dc) [0x4b92dc]
[ 80144.168] (EE) 8: /usr/bin/X (RRGetInfo+0x88) [0x4f66e8]
[ 80144.168] (EE) 9: /usr/bin/X (0x400000+0xfd4b9) [0x4fd4b9]
[ 80144.169] (EE) 10: /usr/bin/X (0x400000+0x3cc3e) [0x43cc3e]
[ 80144.169] (EE) 11: /usr/bin/X (0x400000+0x2c1ba) [0x42c1ba]
[ 80144.169] (EE) 12: /lib64/libc.so.6 (__libc_start_main+0xf5) [0x7f845ce7dbe5]
[ 80144.169] (EE) 13: /usr/bin/X (0x400000+0x2c501) [0x42c501]
[ 80144.169] (EE) 
[ 80144.169] (EE) Segmentation fault at address 0x0
[ 80144.169] (EE) 
Fatal server error:
[ 80144.169] (EE) Caught signal 11 (Segmentation fault). Server aborting
[ 80144.169] (EE) 
[ 80144.169] (EE)