*snip*

Actually I'm not sure about that...

My first guess would also be AddHandler/AddType. Did you test it?
I think you rather added those directives to the httpd.conf for a certain directory instead of the .htaccess. That would explain why it isn't working anymore.

*snip*

Actually I'm not sure about that...

You configured apache to parse php scripts in html files? Dude, that is a huuuuuge security hole if you allow for any user generated content to show up.