When I hit the moolet page directly I get a blank white page which is good. If there was an error it would show up here
http://www.celestinecommunity.de/modules/mod_moolet_recent_visitors/mod_moolet_recent_visitors.inc.php?I was try this. You are loading in a mootools file from
rokbox - mootools-release-1.11.js
I have way of knowing if this is a fully packed file or just a partial for this module. I would turn module rokbox OFF and any other mootools module off for the testing page you sent me to. Then I would turn on load mootools _script_ from one of the moolets. Also only load one of them for the test page as trying to debug two at the same time is near impossible
if you can do that and and let me know I will go back and look