LAOS Laser

We have taken the convention to have discussions on the website in english.
But a funny thing happens.
When you edit a page, all headings in the blue LAOS Laser bar are in english.
Overview-Activity-Issues etc

But when you visit the wiki as a normal user, on http://redmine.laoslaser.org/projects/laos/wiki
they appear in dutch.
Overzicht-Activiteit-Incidenten etc.
(not always, seems to depend on cookies)
Rather confusing, should all be in english

Is there a global setting that can be changed?
If not I voluteer to change all settings to english (if someone tells me where).