SRG Clean Archives makes Atahualpa's Page Menu Bar disappear in Firefox and Chrome, not in IE.

You can see this for http://www.alte-sprachen.de/?page_id=674

Appreciate help!-)

in safari, I see the menu for a moment then it vanishes. I'd look at the settings and CSS for the plugin.
where did you get the plugin from?

From what I can find that plugin is about 4 years old and the latest version is stated to work in WP 2.6 and 2.7.