Tidy isn't Tidy-ing

I'm trying to use the PHP Tidy extension for php4.  I've got the module 
installed and loaded properly and a call to phpinfo() shows that the 
extension is loaded correctly.  I've placed the following directives in 
my php.ini file:

tidy.default_config = /etc/php4/apache2/tidy.cfg
tidy.clean_output = On

However, none of my generated HTML is cleaned up using Tidy.

I've restarted apache several times and I've also enabled output 
buffering in the php.ini

Is there something that I'm overlooking?  Thanks for your help.