Rails update_attribute does not save

I ran into a quirk. I have a GuardianUpdate model with a "read" field that is logical. When I go to call update_attribute (: read, true) on a record, the rails cannot actually update the record.

Here is my console output:

1.9.3p0 :026 > g = GuardianUpdate.find(1)
  GuardianUpdate Load (0.7ms)  SELECT `guardian_updates`.* FROM `guardian_updates` WHERE `guardian_updates`.`id` = 1 LIMIT 1
 => #<GuardianUpdate id: 1, update_id: 2, guardian_id: 11, read: true, created_at: "2012-04-21 04:06:45", updated_at: "2012-04-21 04:06:45"> 
1.9.3p0 :027 > g.update_attribute(:read, false)
   (0.3ms)  BEGIN
  Update Load (0.4ms)  SELECT `updates`.* FROM `updates` WHERE `updates`.`id` = 2 LIMIT 1
   (0.1ms)  COMMIT
 => true 
1.9.3p0 :028 > g.reload
  GuardianUpdate Load (0.5ms)  SELECT `guardian_updates`.* FROM `guardian_updates` WHERE `guardian_updates`.`id` = 1 LIMIT 1
 => #<GuardianUpdate id: 1, update_id: 2, guardian_id: 11, read: true, created_at: "2012-04-21 04:06:45", updated_at: "2012-04-21 04:06:45"> 
1.9.3p0 :029 > 

As you can tell, there are no UPDATE sql statements. Here is my GuaridanUpdate model:

class GuardianUpdate < ActiveRecord::Base
  belongs_to :update
  belongs_to :guardian
end

Any thoughts?

I should mention that update_column (: read, true) works, no problem.