I've been using prefork MPM and suPHP for quite a while, and recently decided to try worker MPM and FCGID. I first used EasyApache to rebuild with FCGID, still using prefork MPM. It built fine, I told it to switch PHP to FCGI, and it did so with no errors, and all my sites still worked. I then ran EasyApache again, and this time selected worker MPM. Now, I get the following in /etc/httpd/logs/error_log on accessing a site:

[Wed Jun 24 03:22:17 2009] [notice] mod_fcgid: call /home/user/public_html/index.php with wrapper /usr/local/cpanel/cgi-sys/php5
[Wed Jun 24 03:22:17 2009] [warn] (104)Connection reset by peer: mod_fcgid: read data from fastcgi server error.
[Wed Jun 24 03:22:17 2009] [error] [client 70.246.118.39] Premature end of script headers: index.php

What have I missed?