openid_profile_preprocess_user_picture expects user picture to be a string.

function openid_profile_preprocess_user_picture(&$variables) {
  $variables['picture'] = '';
  if (variable_get('user_pictures', 0)) {
    $account = $variables['account'];
    if (!empty($account->picture) && file_exists($account->picture)) {
      $picture = file_create_url($account->picture);
    }
    // Add support for external user pictures
    elseif (!empty($account->picture) && valid_url($account->picture)) {
      $picture = $account->picture;
    }
    elseif (variable_get('user_picture_default', '')) {
      $picture = variable_get('user_picture_default', '');
    }

If you have a proper user picture, $account->picture is a file stdClass, not just a string, so you actually get a notice back:

Warning: file_exists() expects parameter 1 to be string, object given in openid_profile_preprocess_user_picture() (line 463 of sites/all/modules/contrib/openid_profile/openid_profile.module).
Warning: preg_match() expects parameter 2 to be string, object given in valid_url() (line 1148 of includes/common.inc).