Not able to edit CustomPress taxonomy

I've created a custom post type with a taxonomy, and now I wish to edit that taxonomy to change the hierarchy. Unfortunately, when clicking the taxonomy link in the admin menu, I get a "Are you cheating?" message (in Swedish, so the translation may be a bit off).

the URL ends in wp-admin/edit-tags.php?taxonomy=Verksamheter&post_type=medlemssida

I read in another thread that taxonomies with capital letters may cause trouble, but CustomPress wont let me change that. Is there another way to change the name that won't cause trouble with the created posts? Or is there another reason for this trouble?