I'm not sure if this needs to be reported in both the Captcha and Arrange Fields modules, so I've done both.
I'm using Drupal 7.18, Captcha 7.x-1.0-beta2, Arrange Fields 7.x-1.9
The captcha is always in the wrong place (top of form, behind fields). See attached screenshot.
I've tried clearing the Captcha placement and Drupal caches to no avail. I've tried allowing a non-admin user with 'Arrange Fields' permissions to place the Captcha field in a Webform, but it just shows up as some text in the Arrange Fields WYSIWYG editor.