Serendipity Forums

I'm working with serendipity 1.1.2 and tinyCME is my editor of choice. When I try to assign a css class to a link the class is displayed at first. When I save the post, though, it is deleted. No CSS class on my link. I can assign a class to a word or something else.

I already checked if there is a plugin that manipulates my links but I did not find any. I had the tooltips plugin installed, but deleted it a few months ago.

Does anybody have an idea what might be wrong?

Thank you
Matthias