WTF Happened to ActionMailer?

For the record, I'm upgrading from 2.0.2

ActionMailer works great on 2.0.2.

I have a thank you email that I want sent as multipart mime so I have

thanks.text.plain.erb and thanks.text.html.erb

Then in my ActionMailer::Base subclass I have

def thanks(order)         recipients order.emailAddress         from "Us <>"         headers "Reply-to" => ""         subject "Thanks for your order"         sent_on         tickets =         body :first_name => order.nameFirst,:quantity => tickets.size, :amount => "$# {order.purchaseTransaction.payment.amount.to_money}", :order_number =>, :ticket_date => tickets.first.validForDate, :order => order   end

I get a single email message with a mime type of text/plain and the contents actually created from the thanks.text.html.erb. Looks like crap. Why in the world was this lovely bit of solid bullet proof functionality messed with at all and how do I get it working again?