CSS at frontend sometimes not loaded

[wellseo]

There is something special on my project www.paratodo.de. I use Collabpress in groups at the frontend. When i click/chose the tab projects, the CSS is not loaded and there are no function to add a project, too. The text is shown, but when i click on it, nothing happens. I can't add a project... But when i refreash the page, everything is fina and works well. Its ever and only, when i load the page the first time. Do anybody have an idea? I use AWS - a Plugin to ajaxify my site, but exclude the collabpress-div... And all other excludes work well... I use no Cache-Plugin. By the way: WP 3.5.1, BP 1.7.2 and Collabpress 1.3.1.2. Any Suggestions why it is, like it is?