go to line 243-245 (i don't know exactly, my file is modded):
$result = $db->query('SELECT g_id FROM '.$db->prefix.'groups WHERE g_title= \''.$db->escape($title).'\' && g_id != \''.$_POST['group_id'].'\'') or error('Unable to check group title collision', __FILE__, __LINE__, $db->error());
should be
$result = $db->query('SELECT g_id FROM '.$db->prefix.'groups WHERE g_title= \''.$db->escape($title).'\' AND g_id != \''.$_POST['group_id'].'\'') or error('Unable to check group title collision', __FILE__, __LINE__, $db->error());