I have found following bug from most of 2checkout patch, this bug will cause order status cannot be updated to 'confirmed' after a successfully transaction.
please change the following line from the 2checkout Payment Extra Info field(config tab of 2checkout):
from this(about line 70)
'x_invoice_num' => $db->f("order_id"),
to this
'x_invoice_num' => $db->f("order_number"),
and save it.