Webform CiviCRM Paypal Button not Working
You may have found a bug in the webform_civicrm module. I don't have a great way of testing paypal right now, but I've just made a few tweaks which I think will help - can you try it out?

Download the patched version here: https://github.com/colemanw/webform_civicrm/archive/ipn.zip