Firstly you have to look at the suite of files that are installed in your moodle directory. There should be an 'login' sub-directory. Open that. This subdirectory contains all the bits of code that handles the logging in of a user into the system, and it is where the problem lies. In that directory there should be a file named "index".

You must open that file with a program that enables you to change the code.

The file commences with the following code (to help you identify the correct file):

<?php // $Id: index.php,v 1.129.2.3 2008/05/18 21:26:57 iarenaza Exp $

require_once("../config.php");

// check if major upgrade needed - also present in /index.php
if ((int)$CFG->version < 2006101100) { //1.7 or older @require_logout(); redirect("$CFG->wwwroot/$CFG->admin/"); }

OK?

Now you have to track down to the following comment:

///Check if the user has actually submitted login data to us

The next few lines should look like this:

if (empty($CFG->usesid) and $testcookies and (get_moodle_cookie() == '')) { // Login without cookie when test requested $errormsg = get_string("cookiesnotenabled"); $errorcode = 1; } else if ($frm) {

Now you have to 'comment out' the bit of evil code so as to make it harmless. This is done by placing a /* at the beginning of the offending code and a */ at the end. Once you have done that, this is what it should look like:

/* if (empty($CFG->usesid) and $testcookies and (get_moodle_cookie() == '')) { // Login without cookie when test requested $errormsg = get_string("cookiesnotenabled"); $errorcode = 1; } } else
*/
If ($frm) {

This simply removes the check to see whether the user has a 'cookie' that proves he/she has been there before. I can't really see why they have included that as it makes no difference and it is clear that some browsers don't keep the cookies in the way that this program anticipates them, hence the problem.

Once you have made the changes and saved them, the program should work OK. Don't worry about making the changes, you can always go back and delete the /* and */ if the worst comes to the worst as this is all you would have added.

btw if you do not want this test it might be easier to change 1-->0
<input type="hidden" name="testcookies" value="1" />
in login/index_form.php

http://moodle.org/mod/forum/discuss.php?d=42266#p238417

Make sure that there are no extra lines at the end of config.php. It needs to end with just ?>
No white spaces or line breaks or anything should appear after these characters.