Sounds like hackers are trying to exploit a race condition.
edit: I just realized this attack could affect bitfog transactions so be careful. I remember seeing a couple reports about people having trouble with bitfog. Since its closed source there is no way to know for sure.
edit 2: Actually its probably not a good idea to move bitcoins at all. All transactions are moving at a snails pace and markets maybe vulnerable.
Sounds like hackers are trying to exploit a race condition.
edit: I just realized this attack could affect bitfog transactions so be careful. I remember seeing a couple reports about people having trouble with bitfog. Since its closed source there is no way to know for sure.
edit 2: Actually its probably not a good idea to move bitcoins at all. All transactions are moving at a snails pace and markets maybe vulnerable.