Textile filter plugin troubles

I decided to, for the first time EVAR, write a plugin. I know, I know, you could hardly accuse me of paucity of ambition, but I sort of know a bit of the strange magical PHP thing and I don’t want this plugin to do a lot – just a way to integrate Textile with WordPress simply.

This is the code that does stuff at the moment:

require_once('classTextile.php');

remove_filter('the_content', 'wptexturize');
remove_filter('the_content', 'convert_smilies');
remove_filter('the_content', 'convert_chars');
remove_filter('the_content', 'wpautop');
remove_filter('the_content', 'prepend_attachment');

add_filter('the_content', 'TextileThis');

(Of course, there’s the other stuff surrounding that. I’m not stupid. Not that stupid.)

I’ve managed to successfully stop the other filters from being applied. But the TextileThis function isn’t being applied, and I see no reason, and when the final line is there the_content outputs nothing at all.

Any ideas?