Rails Ruby on Rails

While upgrading one of my apps, I ran into some trouble with something which was recently fixed in the rails 3-0-stable branch. Upgrading, however, required using arel 2.0.0+. Once I upgraded to arel 2.0.0, I ran into all kinds of bugs. Here is one which I can't seem to figure out.

irb(main):053:0> Order.joins(:client => :country).where(:status => "completed").where(:completed_at => Time.now.beginning_of_day..Time.now.end_of_day).where(:clients => { :countries => { :iso => ["US"] }})
SQL (1.4ms)  SHOW TABLES
Order Load (4.4ms)  SELECT `orders`.* FROM `orders` INNER JOIN `clients` ON `clients`.`id` = `orders`.`client_id` INNER JOIN `countries` ON `countries`.`id` = `clients`.`country_id` WHERE (`orders`.`status` = 'completed') AND (`orders`.`completed_at` BETWEEN '2010-09-28 23:00:00' AND '2010-09-29 22:59:59') AND (`countries`.`iso` IN (0))

When running this query, it replaces anywhere from one to three objects with zeros, then starts with the rest of the array. Here is one with four:

irb(main):054:0> Order.joins(:client => :country).where(:status => "completed").where(:completed_at => Time.now.beginning_of_day..Time.now.end_of_day).where(:clients => { :countries => { :iso => ["US", "CA", "MX", "JP"] }})
SQL (1.9ms)  SHOW TABLES
Order Load (5.7ms)  SELECT `orders`.* FROM `orders` INNER JOIN `clients` ON `clients`.`id` = `orders`.`client_id` INNER JOIN `countries` ON `countries`.`id` = `clients`.`country_id` WHERE (`orders`.`status` = 'completed') AND (`orders`.`completed_at` BETWEEN '2010-09-28 23:00:00' AND '2010-09-29 22:59:59') AND (`countries`.`iso` IN (0, 0, 0, 'JP'))

I have narrowed it down to only associations, because calling Country.where(:iso => "US") or Country.where(:iso => ["US"]) will work:

irb(main):055:0> Country.where(:iso => "US")
Country Load (1.7ms)  SELECT `countries`.* FROM `countries` WHERE (`countries`.`iso` = 'US')
=> [#<Country id: 226, iso: "US", name: "United States", iso3: "USA", numcode: 840>]

irb(main):056:0> Country.where(:iso => ["US"])
Country Load (2.0ms)  SELECT `countries`.* FROM `countries` WHERE (`countries`.`iso` IN ('US'))
=> [#<Country id: 226, iso: "US", name: "United States", iso3: "USA", numcode: 840>]

Any ideas?