Permission to edit own unpublished content (only)?
hook_node_access() to the rescue!  You need to create a new module to do this.  In the new module's .module file you'll need to put this:

function YOUR_MODULE_node_access($node, $op, $account) {
  // Deny updating the content if it's a published poll
  if ($node-&gt;type == 'poll' &amp;&amp; $node-&gt;status &amp;&amp; $op == 'update') {
    drupal_set_message('This poll has been published, you may not make changes to it.','error');
    return NODE_ACCESS_DENY;
  }
}