gdm issue results in black screen during logging out

root      8678     1  0 Sep29 ?        00:00:00 gdm
root      8693     1  0 Sep29 ?        00:00:00 /usr/lib/gdm/gdmopen -l /bin/sh -c /usr/bin/whiptail --yesno 'There already appears to be an X server running on display :0.  Should another display number be tried?  Answering no will cause GDM to start the server on :0 again.  (You can change consoles by pressing Ctrl-Alt plus a function key, such as Ctrl-Alt-F7 to go to console 7.  X servers usually run on consoles 7 and higher.)' 16 70
peterm   20623  8678  0 08:03 ?        00:00:00 gdm
root     21275 20623  0 08:35 tty16    00:00:14 /usr/bin/X :0 -br -audit 0 -auth /var/lib/gdm/:0.Xauth -nolisten tcp
peterm   22903 22884  0 15:16 pts/0    00:00:00 grep gdm
root     24153     1  0 Oct01 ?        00:00:00 /usr/lib/gdm/gdmopen -l /bin/sh -c /usr/bin/whiptail --yesno 'There already appears to be an X server running on display :0.  Should another display number be tried?  Answering no will cause GDM to start the server on :0 again.  (You can change consoles by pressing Ctrl-Alt plus a function key, such as Ctrl-Alt-F7 to go to console 7.  X servers usually run on consoles 7 and higher.)' 16 70
root     24413     1  0 Oct05 ?        00:00:00 /usr/lib/gdm/gdmopen -l /bin/sh -c /usr/bin/whiptail --yesno 'There already appears to be an X server running on display :0.  Should another display number be tried?  Answering no will cause GDM to start the server on :0 again.  (You can change consoles by pressing Ctrl-Alt plus a function key, such as Ctrl-Alt-F7 to go to console 7.  X servers usually run on consoles 7 and higher.)' 16 70
root     24440     1  0 Oct05 ?        00:00:00 /usr/lib/gdm/gdmopen -l /bin/sh -c /usr/bin/whiptail --yesno 'There already appears to be an X server running on display :0.  Should another display number be tried?  Answering no will cause GDM to start the server on :0 again.  (You can change consoles by pressing Ctrl-Alt plus a function key, such as Ctrl-Alt-F7 to go to console 7.  X servers usually run on consoles 7 and higher.)' 16 70
root     24442 24440  0 Oct05 tty14    00:00:00 /usr/lib/gdm/gdmopen -l /bin/sh -c /usr/bin/whiptail --yesno 'There already appears to be an X server running on display :0.  Should another display number be tried?  Answering no will cause GDM to start the server on :0 again.  (You can change consoles by pressing Ctrl-Alt plus a function key, such as Ctrl-Alt-F7 to go to console 7.  X servers usually run on consoles 7 and higher.)' 16 70