error message when activating new plugin

I just installed a facebook like this plugin and a twitter tweet plugin both made by the came author. When both plugins, after I activate them and go to the setting page, I get this warning message at the top of the page:

Warning: session_start() [function.session-start]: Cannot send session cache limiter – headers already sent (output started at /home1/mindstre/public_html/wisdomangermanagement/wp-content/plugins/twitter-tweet-button/inc/main_class.php:54) in /home1/mindstre/public_html/wisdomangermanagement/wp-content/plugins/si-captcha-for-wordpress/si-captcha.php on line 763

Any ideas what I should do?