CSS not loading

hi, sorry to bother you guys, but I’ve been looking the whole day for a solution but couldn’t find one.

My site is working perfectly, except plugins doesn’t load their CSS-files. The website loads the css file without problems, but plugins won’t.

Here is an example: http://de.rundertisch.org/?page_id=128

As you can seem, the CSS loads fine on the page, but the calendar (Events Calendar from Luke Howell) is totally unformatted as if there was no CSS file. But i already checked, and the css files are there.

Only thing i can imagine is that I had to update the wordpress url with:

update_option('siteurl','http://example.com/blog');
update_option('home','http://example.com/blog');

so in the beginning it was: http://rundertisch.org/de and i changed it to: http://de.rundertisch.org

Thanks in advance