I went to the bike shop when they opened at noon. The guy seemed to know what he was doing and was even kind not to charge me. The problem, however was not only correct tension, but the fact that the spokes were too weak. I foresee problems will repeat themselves until I get a new wheel or have a new wheel built with the right spokes (that I have to get from Denmark). I'm randomly meeting my mother in Myanmar in March, so if only I can make it there she can bring new parts from Denmark... though still 2,000k to get there...