XML-RPC and Atom client setup
For those of you who use an external blogging client or anything that uses Movable Type’s XML-RPC or Atom APIs, you have to do one more step (detailed in the entry “Getting started with MT 3.2”) after upgrading to get your clients working again
Source: http://www.sixapart.com/movabletype/beta/2005/07/xml-rpc_and_ato.html