I have the same problem loging with yahoo. For me it shows this error.
Warning: strpos() [function.strpos]: Offset not contained in string in /home/content/40/10621940/html/wp-content/plugins/wordpress-social-login/hybridauth/Hybrid/thirdparty/OpenID/LightOpenID.php on line 87
Warning: Cannot modify header information – headers already sent by (output started at /home/content/40/10621940/html/wp-content/plugins/wordpress-social-login/hybridauth/Hybrid/thirdparty/OpenID/LightOpenID.php:87) in /home/content/40/10621940/html/wp-includes/pluggable.php on line 680
Warning: Cannot modify header information – headers already sent by (output started at /home/content/40/10621940/html/wp-content/plugins/wordpress-social-login/hybridauth/Hybrid/thirdparty/OpenID/LightOpenID.php:87) in /home/content/40/10621940/html/wp-includes/pluggable.php on line 681
Warning: Cannot modify header information – headers already sent by (output started at /home/content/40/10621940/html/wp-content/plugins/wordpress-social-login/hybridauth/Hybrid/thirdparty/OpenID/LightOpenID.php:87) in /home/content/40/10621940/html/wp-includes/pluggable.php on line 682
Warning: Cannot modify header information – headers already sent by (output started at /home/content/40/10621940/html/wp-content/plugins/wordpress-social-login/hybridauth/Hybrid/thirdparty/OpenID/LightOpenID.php:87) in /home/content/40/10621940/html/wp-includes/pluggable.php on line 876