I have the same problem, now 48 hours. I decided to investigate and pulled all the TXs from
https://data.mtgox.com/api/0/bitcoin_tx.php - i found my receiving address in there. I then transmitted all of the transactions to the network.. the outputs on mine and over 200 other ones have already been spent, and the network rejects them immediately.
Seems like a problem with double spending, which would imply a race condition within their code, so no kind of locking in place to prevent this happening.
Pretty sure this has been discussed in the past, and the concensus is that when a transaction becomes 'stuck' for some reason that's not clear to me (bug? fee too low?) and never makes it to the block chain, then Gox will invalidate the stuck transaction (by creating a 'pay-to-self' transaction using the same outputs) before trying again.