Aha, here is the problem I think!
"Posted by Gustaf Neumann on 05/14/09 05:53 AM
A small followup: in order to develop a new viewer for e.g. categories, i would recommend to disable for the development the includelet caching (set parameter "cacheable" of the includelet "categories" to false). Otherwise you have to flush the page fragment cache entries frequently to check the results of your changes."
https://openacs.org/forums/message-view?message_id=2752305
