Q:

CodeIgniter Blank Page

n00b here. After searching the forums I have not yet come across this problem as I am experiencing it. 
I have a CI site that was working correctly until about three days ago. My problem is as follows:
On button click - Page Loads correctly.
On Enter press - CI Blank Page of Death loads.
For example: When I login, after the login process has run it must reroute me to the Dashboard, unless I still have a temporary password where I get rerouted to the "Change Password" screen first and then to the Dashboard. 
AS LONG AS I USE THE BUTTONS AND CLICK THEM EVERYTHING WORKS.
On ENTER PRESS, I get the Blank Screen of Death.
However, on TAB to BUTTON and then ENTER it works.
The problem is not consistent however. I have some processes that do not have views attached and NONE of them will run - hit ENTER and get blank. They are all failing on ENTER PRESS.
I am slowly going off my trolley. Logging is ON, Directories for cache and logs are 775. NOTHING is showing in my logs...

A:

First Try to active error handlers for displaying of errors for addittional info to post here what error is occuring..
 // change settings for error handler to show errors
        // $this setup is used for checking errors for development to be shown.... 
        ini_set('display_errors', 1);
        error_reporting(E_ALL);

by the way if your using CI version 2 higher
you can see it in its index.php file an configuration for displaying error also.
define('ENVIRONMENT', 'development'); //just set up environtment to development

A:

Even though there are accepted answers I wanted to add a way that worked for me to figure out this problem.
Usually the "Blank Page" indicates a PHP parsing error somewhere in the code.  Strange thing for me was that on my local MAMP based test server the code ran fine.  I FTP it to my hosted server and all of a sudden, blank page of death.
Even though I had errors on, log errors on, display errors on, nothing appears in any log file.
I was able to find the error by a funny little trick.   I added an echo line in CodeIgniter.php in the system/core.   Obviously hacking the core was not a great idea but all I wanted to do was to see how far it was getting in the load process.
When my echo appeared after trying to load a page on the remote hosted server it also displayed the parsing problem in a derived controller!  Not sure why the error did not come out without the "echo" added.  But adding it seemed to trigger some output to be generated, IE my echo line and the PHP parse error was appended.
Not sure if this will help anyone but it turned out to be a nice easy way to find the error which only showed on the remote server. 
Obviously, don't forget to put your core file back to its original state without the echo.

