3.5.2 problems

Hi – I’m new to the forum, so thanks in advance for any help you can give me. I’ve recently taken over a wp website and the first thing I did was update to the latest version. I’ve since realised that this wasn’t a good idea as I am now unable to insert media or links into my posts. I’ve tried de-activating plug ins which didn’t work, and there is no update to the template installed on the site. I’ve tried adding the code
define(‘CONCATENATE_SCRIPTS’, false ); to the wp-config.php file, but nothing has worked. Please can anyone help – I’m a relative newbie and would appreciate advice in a non-techie way? Is there another update imminent that would solve this?

Many thanks
wp