WYSIWYG's TinyMCE toolbar looks broken in Arthemia

Hi,

I'm using this great theme or a wiki and community site on microfinance. To allow also non-technical users to contribute to the wiki, I employ TinyMCE via the WYSIWYG API.

While everything looks perfect in Garland, the "Paragraph"-format drop-down menu looks broken in Arthemia (see attached picture for the Firefox view, IE is even worse).

I already spent several hours digging through CSS, but I couldn't find the single style that breaks it.

Any ideas or anyone with similar problems?

Thanks,

Basanta