aux power for board

Hi all I have a problem with powering the Ardiuno board when I plug in the jack plug (+ tip) the power led does not light the board appears dead .Have also tried to apply voltage to the outside of the jack plug but to no avail .Any ideas?

Jon

Did you switch the jumper from the two pins closest to the USB plug to the two closest to the external jack?

Doh

now there's just this serial problem??????????????