Cannot Install or update WordPress plugin & WordPress core

Cannot Install or update WordPress plugin & WordPress core

When i try to update any plugin it will show blank page on the right. No
errors displayed. Uninstall is working perfectly. Cannot install new
plugin & cannot update WordPress Core
NO ERRORS DISPLAYED, only white page on right (you can see side menu of
dashboard)
Hosting my Files in VPS - Centos 6 - Apache 2.4.6
Recently i updated PHP 5.3.26 to PHP 5.4.17
I tried Changing Owner Permission to Apache. (i was unable to login - then
changes back to my username)
I tried chmod 777 no use.
I tried adding in wp-config.php - define('FS_METHOD', 'direct'); & chmod
777 to wp-content directory.
Please help.