by Pavel Krejci.
Hello,
this looks like when the YUI javascripts fail to load - which can be caused by old/misconfigured server software or maybe incompatible theme.
Non-standard theme adds additional complexity to this error. Try to switch back to the "Standard" theme by adding
$CFG->theme = 'standard';
to the bottom of your Moodle config.php file to force the standard theme.
To check for YUI loading errors display the HTML source of the page with admin menu, locate and check if the linked YUI javascript files are accessible - ie. if the generated URLs are correct. This can be easily done in Chrome tools (F12) - Resources tab or Console. See attached screenshot.