I only have one group listed in the tree-view. Even though more groups are displayed in the left side-bar. Does anybody know where this data is stored? Perhaps in the database? Then I can delete the groups through pgadmin.

I tried Mike's solution on a new database, and it seems ineffective. While deleting the groups removes them from the tree-view; the corresponding menu-items in the sidebar do not vanish.

Same problem in unable to remove the items from the sidebar - and every time you re-enable the portals you gain another set of entries in the sidebar

I can confirm the above behaviour, I found it best to start from a new database for production; and do my development on a different database. Also make many many backups while installing modules, so you can always revert in case something goes wrong.