segfaults with 2.0.2 and named routes

This is a really strange one. Latest ruby stable, rails 2.0.2, debian
sid. About a dozen plugins installed which makes it more difficult to
track down...

In routes.rb I have the following:

map.resources :profiles, :controller => :user_profiles

So I'm using profile_path(user_obj) in my views. And I'm using
acts_as_commentable.

profile_path(current_user), where current_user is from
acts_as_authenticated works fine. But when I get a user object from
Model.comments.users, and pass that to profile_path, immediate
segfault. Using ruby-debug to step through a line running mongrel
only confirms this is where it's bombing, I haven't been able to track
it down further yet. Even more interesting is that it only segfaults
the second time the code is run (second page load in the same
process).

Ya so I know what to do next, but though I'd post this in case someone
might have an idea where to look first.

Chris