I had exactly the same problem with my Sheevaplug. I repaired mine with an external 5V/3A power supply and a fitting connector.

Connector:
http://www.conrad.at/ce/de/product/733946/EINBAUBUCHSE-MIT-SCHALTKONTAKT-21-MM/0223020

Power Supply:
http://www.conrad.at/ce/de/product/510820/Dehner-SYS1308-Netzt-fests-5V15W/2110120