mapOrphan overflow, removed 1 tx
First of all, backup your wallet in a couple of places...

If you are in linux, move your ~/.bitcoin to ~/.bitcoin_old, once you've done that start bitcoin-qt, wait another day for the whole blockchain to download. This time it should be working OK.
Replace the wallet in ~/.bitcoin with your wallet in ~/.bitcoin_old and resync.

Remember to have your wallet.dat saved before you do anything (I would have 2 or 3 copies in different places (usb, external HD, etc ...)