"Multiple default values" with Rails migration

I am running the following migration with PostgreSQL 8.2.5. It works
fine on my Windows machine, but gives me the below error on Linux
CentOS 4.3. Any ideas? Thanks, Chirag

class CreateUsers < ActiveRecord::Migration
  def self.up
    create_table :uers do |t|
      t.column :timestamp, :timestamp_with_time_zone
      t.column :userval, :integer, :limit => 1, :null=> false #will
use smallint becuase of plug-in

  def self.down
    drop_table :users

== CreateUsers: migrating