single table inheritance problem

Hallo,

I am having a very strange Problem with STI in my application.

setup:
- two tables one called "wikis" on called "categories" with a hbtm
relationship.
- the wikis table is the sti one with a model PageWiki being extended
from Wiki (and the correspondig type column)

Following happens:
- server restart
- get :wikis, :show_pages
- in show_pages the first line says PageWiki.find(:all)
! Now I get the following error

LoadError in WikisController#list_pages
app/models/page_wiki.rb to define PageWiki // (it is of course defined
there )

If i call the page again everythings works as it should be and the the
error message never appears again until the server restarts
BUT !
When I now try to add categories to my wikis with

@wiki = Wiki.find(params[:wiki])
@category = Category.find(params[:id])
@wiki.categories << @category unless
@wiki.categories.index(@category)

I get the VERY unhelpful error messages telling me

ActiveRecord::AssociationTypeMismatch
in WikisController#add_category
Category expected, got Category

This error does not appear if do not call the list_pages method
before.

If I change the line PageWiki.find(:all) to
Wiki.find(:all, :conditions =>"type='PageWiki'") it all works.

Does anybody have any ideas what happens here?
Thanks a lot for any help.

migo

I have to correct myself here.
Although things work (dont work) in the order described the
Category expected, got Category
Error message still appears after a while and then continues to be
there until a server restart.
Now this is really a problem! A bit of googling revealed that is has
to do with the plugins used.
So these are the plugins used:
acts_as_versioned
acts_as_tree
globalize

Any idea ?