Zend Framework can't find standard view helpers

I'm trying to use a View helper inside a view. I put

echo $this->formCheckbox('foo');

in the view, but it errors out and tells me FormCheckbox.php /application/modules/user/views/helpers/FormCheckbox.php can't be found. Why isn't it loading Zend_View_Helper_FormCheckbox in /Zend/View/Helper? The manual states

The default helper path always points to the Zend Framework view helpers, i.e., 'Zend/View/Helper/'. Even if you call setHelperPath() to overwrite the existing paths, this path will be set to ensure the default helpers work.

From stackoverflow

• To use helpers in my views I use:

  <?= $this->LinkTo('css/general/screen.css'); ?>
  

  Is your helper 'FormCheckbox' with a capital F?

  : In both cases, it looks for FormCheckbox.php with a capital F. All the standard helpers arent working, including LinkTo.
  From philm