Craftsmann

Yes it’s OK

Yes, lines are active and defined by unique phrases

After deleting cookies (using Firefox dev bar) and refreshing admin area nothing happens. I stay authorized.

Ok
option 1 suits me for now. If need additional info I can provide it.

News ??
After define or comment those constants in wp-config.php everything works now.

define('AUTH_KEY',
define('SECURE_AUTH_KEY',
define('LOGGED_IN_KEY',
define('NONCE_KEY',
define('AUTH_SALT',
define('SECURE_AUTH_SALT',
define('LOGGED_IN_SALT',
define('NONCE_SALT',

But I discard those changes and comment line 9 – it also was successful, now I can log in to admin area. Besides after disabling line 45 in admin-filters.php everything works fine.
//add_filter('locale', array(&$this, 'get_locale'));

So there are two options when site works
1. When constants are defined not by default values or commented
2. When commented line 45 in admin-filters.php

Yes, sure.

Yes, I can.
Also I can log in in front-end but when I try to go to admin area I get log in window again.

Unfortunately no, just nothing happens.
1. But my local site on my local desktop works fine, I have problem only on my hosting site, may be something wrong with url rewrite rules and cookies (I mean adding language to url)…
2. Polylang is the only one active plugin on both my sites.
3. Where in DB polylang store its settings? I’ll try to drop them.

This line works! In addition I found out the cause of error – this is conflict with Tabbed Widgets plugin.
So many thanks for your help!

Thanks for the quick answer! No, I don’t have any preview plugins. But I have to say I have a lot of plugins on my test environment ? which one is bad is difficult to say.
After brief view of plugin code I suppose that it happened because when I click Save hook named widgets_init begins to run but global $polylang was not declared as object at this moment. (also after unsuccessful save all my widget page in admn area crashed with this error ). I’ve changed piece of code in Polylang’s constructor in that way and now everything is ok in my case. But I’m note sure that this is the right solution so far ??

if (is_admin()) {
        require_once(PLL_INC.'/admin.php');
	new Polylang_Admin();
        require_once(PLL_INC.'/core.php');
        $polylang = new Polylang_Core();
}

I have the same problem. I have wp_head() before </head> in my theme.