getting error in error_log in root

got this error in root of the site in an error_log
[15-Feb-2014 08:10:07 UTC] PHP Fatal error: ob_start() [ref.outcontrol]: Cannot use output buffering in output buffering display handlers in /home/XXXXXXXX/public_html/wp-content/plugins/twitter-facebook-google-plusone-share/tf_display.php on line 372

How to fix this please?

https://ww.wp.xz.cn/plugins/twitter-facebook-google-plusone-share/