That is what I was thinking, but how to stop the tx of this? Do I have to go through the rigamarole of downloading my blockchain.info wallet into QT, deleting the transactions, then re-uploading it?
I am not sure if blockchain.info rebroadcasts unconfirmed tx.
If it doesn't, you can just wait for a day or so, and everything will be back to normal.
You only need to wait at this moment.
And no worries, your bitcoin is safe.