This fix worked for me after upgrading to php 5.3. I got the errors:
Warning: Parameter 1 to ec3_filter_posts_where() expected to be a reference, value given in /home/klangart/public_html/wordpress/wp-includes/plugin.php on line 166
Warning: Parameter 1 to ec3_filter_posts_join() expected to be a reference, value given in /home/klangart/public_html/wordpress/wp-includes/plugin.php on line 166
Warning: Parameter 1 to ec3_filter_posts_groupby() expected to be a reference, value given in /home/klangart/public_html/wordpress/wp-includes/plugin.php on line 166
Warning: Parameter 1 to ec3_filter_posts_fields() expected to be a reference, value given in /home/klangart/public_html/wordpress/wp-includes/plugin.php on line 166
But I had to remove the "&" at this functions:
function ec3_filter_the_content($post_content)
function ec3_filter_posts_where($where)
function ec3_filter_posts_join($join)
function ec3_filter_posts_orderby($orderby)
function ec3_filter_posts_groupby($groupby)
function ec3_filter_posts_fields($fields)
There are other filter functions with the same syntax, which I didn't change, because it seems to work so far...
Thanks Rightintwo for the hint. "function ec3_filter_post_limits" doesn't exist in my "eventcalendar3.php".