When I turn off the lcd monitor by power switch and turn it on again - the desktop disappear.
kdm.log:
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Backtrace:                                                                                                                                             
0: /usr/bin/X (xorg_backtrace+0x28) [0x4a4348]                                                                                                         
1: /usr/bin/X (0x400000+0x654a9) [0x4654a9]                                                                                                            
2: /lib/libpthread.so.0 (0x7f3e1b659000+0xe950) [0x7f3e1b667950]                                                                                       
3: /usr/lib64/xorg/modules/extensions/libglx.so (0x7f3e198ec000+0x38b4e) [0x7f3e19924b4e]                                                              
4: /usr/bin/X (FreeClientResources+0xe6) [0x44e3f6]                                                                                                    
5: /usr/bin/X (FreeAllResources+0x3e) [0x44e4ae]                                                                                                       
6: /usr/bin/X (0x400000+0x248ce) [0x4248ce]                                                                                                            
7: /lib/libc.so.6 (__libc_start_main+0xfd) [0x7f3e1a858aed]                                                                                            
8: /usr/bin/X (0x400000+0x24439) [0x424439]
Segmentation fault at address 0x3c80000034c

Fatal server error:
Caught signal 11 (Segmentation fault). Server aborting
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