[CentOS] -bash: /bin/grep: cannot execute binary file

Hi all,I have problem on CentOS 5.2

while everything is working great,suddenly i have this error when i login my server,

sudo su - -bash: /bin/egrep: cannot execute binary file -bash: /bin/egrep: cannot execute binary file -bash: /bin/egrep: cannot execute binary file -bash: /bin/hostname: cannot execute binary file -bash: /bin/grep: cannot execute binary file -bash: /bin/grep: cannot execute binary file -bash: /bin/grep: cannot execute binary file -bash: /bin/grep: cannot execute binary file [root@centos ~]#

and when i try use vi editor,i have same error like above

-bash: /bin/vi: cannot execute binary file

What is problem do you think ? i searched this problem on google but did not found any reasonable answer.

Thanks all for all helps.