There seems to be a major bug in the Mac version, it keeps showing and error in the database and makes me re-download the blockchain everytime I try to open the client. I had to revert back to the old version to be able to download the blockchain and access my wallet.
Most likely explanation is one of your blockchain data files is corrupted, but the old version doesn't care. You might be serving up a corrupted blocks to anybody who downloads from you, but you wouldn't notice that either.