I've got a copy of linux mint 10 (julia). I've got apache2 and php packages installed.
the php5 files are in /etc/apache2/mods-enabled.
Browse to a directory with an 'index.php', and the php file is served up, not executed.
The access log has
127.0.0.1 - - [29/Mar/2011:13:09:40 -0400] "GET /typo3/index.php HTTP/1.1" 200 33147 "-" "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.15) Gecko/20110303 Linux Mint/10 (Julia) Firefox/3.6.15"
and the error log has nuthin.
php5.conf contains the following, which would seem to exclude .php, but adding it to the match didn't help.
<IfModule mod_php5.c>
<FilesMatch "\.ph(p3?|tml)$">
SetHandler application/x-httpd-php
</FilesMatch>
<FilesMatch "\.phps$">
SetHandler application/x-httpd-php-source
</FilesMatch>
# To re-enable php in user directories comment the following lines
# (from <IfModule ...> to </IfModule>.) Do NOT set it to On as it
# prevents .htaccess files from disabling it.
<IfModule mod_userdir.c>
<Directory /home/*/public_html>
php_admin_value engine Off
</Directory>
</IfModule>
</IfModule>
The same file on an Ubuntu system I have to hand is
you might try and see if that works.