Bitcoin Exchanges Under ‘Massive and Concerted Attack’
It's interesting to watch actually, submit a transaction to the network at the moment and there's a rogue node that will mess with the padding of the signatures and rebroadcast it <i>faster</i> than the original. It confuses the reference client into duplicate display, which is what Gox is relying on for the failed/success display. That they're winning races over the normal related transactions isn't that unnatural as the transaction processing stuff has a 100ms sleep() in the middle of it.