Just been doing more testing. I've noticed: http://openidenabled.com/php-openid/trunk/examples/server/server.php Does not work with Plaxo's "2.0" openid implementation: http://flickr.com/photos/hendry/2243569287/ Yahoo's "2.0" openid service seems to work however. Are they perhaps using an old library? http://www.plaxo.com/api/openid_recipe With thanks,