Can you confirm it is the socket rather than the power lead ?
If it is the socket, it's probably got banged at some time, which has damaged the solder joint to the pcb. If this is the case and it is in warranty, you should send it in. If it is not in warranty, you have a choice between sending it in, or having a tech-y person take the unit apart and trying to resolder it.
If it is the power lead, a new power unit is indicated.
