I've just posted a C++ XMLRPC implementation to the wiki; as with a little modification, I've managed to get the XmlRpc++ library to communicate with SL (the modifications are posted with the test application)
Steps are pretty self explanatory; download XmlRpc++, unpack, replace XmlRpcValue.cpp with the one listed; compile, test & enjoy.
http://secondlife.com/badgeo/wakka.php?wakka=XMLRPCImplementations
-Adam