Hey,
Using Ruby 1.8.5, postgres-pr-0.4.0, activerecord-1.15.2, Rails 1.2.2
and PostgreSQL 8.2.3. I'm following the O'Reilly book "Ruby on
Rails", so you can tell I know precious little of what I'm doing 
Well, I've created some models, and was working through examples, and executed the following from a console:
show = Slideshow.find 1
=> #<Slideshow:0x7f2d7588 @attributes={"name"=>"Interesting pictures", "id"=>"1", "created_at"=>"2007-02-17 19:41:30.703"}>
show.slides.first.photo.filename
=> "balboa_park.jpg"
show.slides.first.move_to_bottom
ActiveRecord::StatementInvalid: PGError: ERROR: argument of AND must be type boolean, not type integer : UPDATE slides SET position = (position - 1) WHERE (slideshow_id AND position > 1) from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/ active_record/connection_adapters/abstract_adapter.rb:128:in `log' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/ active_record/connection_adapters/postgresql_adapter.rb:152:in `execute' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/ active_record/connection_adapters/postgresql_adapter.rb:162:in `update' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/ active_record/base.rb:497:in `update_all' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/ active_record/acts/list.rb:210:in `decrement_positions_on_lower_items' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/ active_record/acts/list.rb:106:in `move_to_bottom' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/ active_record/connection_adapters/abstract/database_statements.rb: 59:in `transaction' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/ active_record/transactions.rb:95:in `transaction' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/ active_record/acts/list.rb:105:in `move_to_bottom' from (irb):3
The error is pretty specific. I'm thinking the where clause should be (slideshow_id NOTNULL AND position > 1)?
Any help?
Thanks, Rob