Getting acts_as_tree to work

I see others have had configuration issues with acts_as_tree and sorted them out, but I can't get it to work. On Rails 2.0.2 I do the usual 'ruby script/plugin install acts_as_tree' which puts acts_as_tree into vendor/plugins.

One respondent said he'd managed to get things to work by altering config.plugins but the comment above config.plugins says # ..By default, all plugins # in vendor/plugins are loaded in alphabetical order.

So it shouldn't be necessary. In any case if I uncomment config.plugins and put act_as_tree in it, the system then complains it can't find acts_as_tree or any of the other things in the config.plugins list.

What do I have to do to get this to work?

Are you successfully loading ANY plugins?


P.S. I started out with acts_as_tree, but ended up going for betternestedset to reduce the number of SQL queries.