Versions 1.2 of the new XML-RPC client/server have been released. Version 1.2 simplifies the creation of XML-RPC messages. Upgrading is recommended but not required.
Messages created by a client of version 1.2 are compatible with all XML-RPC servers. Client and server don't have to be of the same version number.
See http://www.thecodemill.biz/services/xml-rpc/ for more details.
An reference implementation of the XML-RPC test suite is available at http://www.thecodemill.biz/RPC2. Point you XML-RPC client to this URL to test your client installation.
/Bart