[RCU] Roundcube "hangs" in settings pages

Hi list

I got a weird problem with my roundcube 0.9.2 installation. If I go to the settings pages and choose any menu item from the left pane (e.g. server-settings) RC hangs forever showing "loading data". The same goes for all plugins settings which have menu items in the left pane. If I click such a menu item all other links in RC are not working anymore. I have to reload the page in browser (ctrl+F5) to use RC again. Webmail itself works fine, it's just the settings pages that seem to be broken somehow in my case. Tried as well a new installation with new mysql database, but the same

Thanks for any idea where to start searching

tobi