I am having the same problem, with the same message, but at block 194995.
was there a hack at that point in the block chain?
did starting again help? it took me a day to get to that point, so I am a bit loathed to start again.
Thank you.
It's probably just a database corruption issue, with resolutions as noted above. There have been no hacks in the blockchain that I know of, besides one years ago when someone created ~2 billion bitcoins (integer overflow exploit), but that block is no longer in the blockchain.
Downloading the blockchain taxes the CPU, network, and disk storage subsystems all at once, and I think this is why many systems have issues with the task. One time, my OSX Lion macbook pro had a hard crash with a mutex spinlock problem when downloading the blockchain. After restart, I found that my blockchain was corrupted, and I had to delete the database files (all but the wallet file in ~/.bitcoin in linux or ~/Library/Application Support/Bitcoin on osx) and restart from scratch, and it worked just fine on the second try.