So, here's the odd behavior I've noticed lately ... whenever you send a $_POST variable to a page named 'name' ... that is, one that would be accessed by $_POST['name'], it doesn't matter what the variable itself contains, WordPress comes up with a 404 page not found.
I've googled and tried grepping my way through my install, but can't seem to find where or why it's catching. Any ideas?
To test this out, give this simple form here a quick test. It links you to the home page of Number 10 Downing Street