I sent a payment of 0.9995 bitcoins back in April to my MtGox account. However I just checked and it has 0 confirmations. Additionally it doesn't show in my wallet or my MtGox account. Is it lost? Can I get it back?
If your transaction from April still has no confirmation, it would be feasible to create another transaction that spends the same input to yourself. You could hope that your new transaction would be verified first, which would invalidate the other transaction and salvage your coins.
Run this option when starting bitcoin-qt:
I've had this exact same issue several times with other coins and it works like magic.