Incompatible with taxonomy_redirect

function theme_tagadelic_weighted($terms) {
  $output = '';
  foreach ($terms as $term) {
    $output .= l($term->name, taxonomy_term_path($term), array('attributes' => array('class' => "tagadelic level$term->weight", 'rel' => 'tag'))) ." \n";
  }
  return $output;
}

This function is incompatible with any module that hooks into the taxonomy system to override the path, for example taxonomy_redirect. Part of the code of taxonomy_redirect resets the weight of the term. I would recommend using variables to define each value required by l() before calling taxonomy_term_path(). The following should resolve the issue..

function theme_tagadelic_weighted($terms) {
  $output = '';
  foreach ($terms as $term) {
    $name = $term->name;
    $weight = $term->weight;
    $path = taxonomy_term_path($term);
    $output .= l($name, $path, array('attributes' => array('class' => "tagadelic level$weight", 'rel' => 'tag'))) ." \n";
  }
  return $output;
}