seems to be an error when it initializes the pull-downs for your text editor.. they all throw errors, when clicked on..
it's prolly fixable, but it would require time to look into it that i don't have at the moment..
you may just be able to get by with a non compressed version of mootools.js instead. i notice you compacted your .js file for that.
ideally, i'd really take all those .js files and make a .gz out of it and serve it up as one big gzipped thingie..Linky Poo™
i do that for my sites and it makes a difference