What could cause apache2 to not run index.php files through PHP FastCGI handler?

I'm wondering whether your use of mod_index is by-passing the vhost for fastcgi (i.e. separate from the vhost that sets the use of the php handler).

This is possibly silly, but try:

<IfModule mod_fcgid.c>
   AddHandler    fcgid-script .fcgi
   IPCConnectTimeout 20
   AddHandler fcgid-script .php
   FCGIWrapper /usr/lib/cgi-bin/php5 .php
   DirectoryIndex index.php
</IfModule>

I've discovered a number of weirdness when Apache modules interact in odd ways. Certainly at times order in the config file is very important.

Oh man, I've been very stupid.

Apparently I just had it misconfigured at one point in time, and my browser had cached the incorrect response.

http://example.com/index.php then worked, probably because I only started trying that after I had gotten FastCGI PHP working, so no incorrect response was in cache.

In other words, the information in my original question is a working configuration for mpm-worker + PHP in mod-fcgid!

Thanks for the effort anyway :-)