Hello Sudan LoCo Team Members ,How are You ?

My Problem this time is 'Simple' I think ..

when I try to Hibernate my Pc 'CTRL + ALT + DEL' nothing happens and the screen goes blank like it is 'Locking' the account .

info :
user@ubuntu:~$ uname -a
Linux ubuntu 2.6.32-24-generic #39-Ubuntu SMP Wed Jul 28 06:07:29 UTC 2010 i686 GNU/Linux
512 MB RAM
1.8 Intel Dual CPU