Cannot send session cache limiter - headers already sent

Hi there

I'm getting the following error

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/myschool/public_html/wp-content/plugins/bp-custom.php:5) in /home/myschool/public_html/wp-content/plugins/events-and-bookings/events-and-bookings.php on line 150

The bp-custom.php custom code as supplied by Ray of CBOX is as follows:

<?php
function eugene_ges_block_external_items( $retval, $type ) {
// if item is an external rss feed, stop it from recording in GES
if ( $type == 'exb' ) {
return false;
}

return $retval;
}
add_filter( 'ass_block_group_activity_types', 'eugene_ges_block_external_items', 10, 2 );
?>

My research points me to two possible errors, both of which I think I have eliminated.
1) a rouge space
2) wp-content file permissions

When I disable the events plugin, I get a the same error, but pointing to the Ultimate facebook plugin, and so on.