Standalone AR Migrations

Hi, I'm trying to utilize AR migrations outside of a rails application
as this sort of thing is valuable in just about any application using a
versioned database. I have seen examples
(http://blogs.pragprog.com/cgi-bin/pragdave.cgi/Tech/Ruby/MigrationsOutsideRails.rdoc)
of calling AR standalone, however; I would like to leverage the up/back
support that you get with AR::Migration instances.

In peeking around the AR source, I saw that the default rake task calls
ActiveRecord::Migrator.migrate and passed in the scripts directory and
optional version number. I created the following simple script:

require "rubygems"
require_gem "activerecord"

ActiveRecord::Base.establish_connection(
  :adapter => "sqlserver",
  :host => "DBI:ADO:Provider=SQLOLEDB;Data Source=localhost;Initial
Catalog=migrate_demo;User Id=someuser;Password=itsasecret;",
  :username => "someuser",
  :password => "itsasecret",
  :database => "migrate_demo")
ActiveRecord::Migrator.migrate("db/", ARGV[0] ? ARGV[0].to_i : nil

I verified the connectivity in IRB (having patched the DBI's ado.rb)
and all is well. When I run the script I get the following (long stack
trace below). I'm hoping someone can with setting up AR properly. The
stack trace is below... Thanks!