[praka123]

^^ you need to have the line
Section "Extensions"
Option "Composite" "enable"
EndSection

NOT in the End.
press ALT+F2 to get run command:
then insert "gksudo gedit /etc/X11/xorg.conf"
edit and save.also make sure you have the module dbe loaded.(Load "dbe")
below is a sample of mine:

Section "Device"
        Identifier      "Intel Corporation 82915G/GV/910GL Integrated Graphics Controller"
        Driver          "i810"
        BusID           "PCI:0:2:0"
        Option "XAANoOffscreenPixmaps" "true"
EndSection

Section "Extensions"
        Option "Composite" "enable"
EndSection

 Option          "AIGLX" "true"