Error parsing Custom Group from Form due to wrong type

See forum:http://forum.civicrm.org/index.php/topic,28493.0.html
Warning: explode() expects parameter 2 to be string, array given in CRM_Core_BAO_CustomGroup::extractGetParams() (line 1429 of civicrm/CRM/Core/BAO/CustomGroup.php).

In CRM/Core/BAO/CustomGroup.php, there is function extractGetParams(&$form, $type). Does a call to $value = CRM_Utils_Request::retrieve($fieldName, 'String', $form); which can return an array.
$value = str_replace("|", ",", $value);
$mulValues = explode(',', $value);

explode seems to fail as it expects a string. need to check / process for array i thing...