Here are some things to try, if you haven't already:
delete all files in the core/cache directory
run setup
turn off the compress_js and compress_css System Settings
clear your browser cache *and cookies*
check the path in the first record of the modx_workspaces table in the DB with PhpMyAdmin
check all the paths and urls in core/config/config.inc.php
If it's not one of those, the most likely thing is a missing or corrupted file or a file in the install. It's less likely if you unzipped the files on the server, but still possible.
Hi!, thanks for your reply!, I tried all of the above but it didn't work, so I investigated a little. I found that the error was caused by the function "mb_strtolower" in the "modfilemediasource.class.php" at "core\model\modx\sources. It said that mb_strtolower was not defined, so the connector returned an error and extjs couldn't work. I installed a new modx in the same server to see if it was a problem with the php configuration but it worked well so now I'm confused why in the main project it says the function is not defined and in a new modx it's not, since its a php function that has nothing to do with modx. I've changed the 2 ocurrences of "mb_strtolower" to "strtolower" and everything's working now.
Newer versions of MODX test for that method. Here's an example from the new code:
$properties['use_multibyte'] = function_exists('mb_strtolower')) ? true : false;
/* ... */
$useMultibyte = $this->getOption('use_multibyte',$properties,false);
/* ... *./
$ext = $useMultibyte ? mb_strtolower($ext,$encoding) : strtolower($ext);
