for the first 2 errors, you just forgot the ';' at the end of debugging lines.
Indeed, now I'm getting lots of debug output, including some serialized data I can not interpret. As far as I can see, "drupal_set_title" is also nowhere referenced. The array segment around the localized "image gallery" string looks like this:
[mission] => [primary_links] => Array ( [menu-29141] => Array ( [minipanel] => galerien [menu_minipanels_hover] => Array ( [position] => Array ( [target] => false [target_custom] => [type] => absolute [corner] => Array ( [target] => bottomLeft [tooltip] => topLeft ) ) [show] => Array ( [delay] => 100 [when] => Array ( [event] => mouseover ) [effect] => Array ( [type] => slide [length] => 0 ) ) [hide] => Array ( [fixed] => true [effect] => Array ( [type] => slide [length] => 0 ) ) [style] => Array ( [name] => light [width] => Array ( [min] => 0 [max] => 800 ) [border] => Array ( [width] => 3 [color] => #d3d3d3 [radius] => 0 ) [tip] => topLeft ) [mlid] => 29141 ) [attributes] => Array ( [title] => Bildergalerien ) [href] => galerie [title] => Galerien ) [menu-38332] => Array ( [minipanel] => reisen [menu_minipanels_hover] => Array ( [position] => Array ( [target] => false [target_custom] => [type] => absolute [corner] => Array ( [target] => bottomLeft [tooltip] => topLeft ) ) [show] => Array ( [delay] => 100 [when] => Array ( [event] => mouseover ) [effect] => Array ( [type] => slide [length] => 0 ) ) [hide] => Array ( [fixed] => true [effect] => Array ( [type] => slide [length] => 0 ) ) [style] => Array ( [name] => light ...
In the surrounding of the string appears the 'menu_minipanels' module; with trial-and-error I disabled this module and immediately got the "normal" titles back. I'm not sure if this suffices for a bug report against 'menu_minipanels', but I'll try it.
Thanks again to you all! -asb