Text break ('read more') function not working

Hi, I wanted to be able to hide and reveal bits of text on this page: http://cargocollective.com/utmt/Gunu-Kim

and followed the instructions found here: http://support.cargocollective.com/discussion/7720/how-can-i-insert-a-page-breaks/p1

but for some reason the revealed text just opens and closes again. Any idea what causes this to happen, and how I can sort it out?

Thanks in advance,
Régis