I just spoke with richie over at bittrex, we had a fair amount of orphan blocks come through earlier, so in the interest of safety, he froze the wallet until we could speak and take a better look at it.. looks like the huge peaks in hashpower and our 1 block difficulty retarget could have been the culprit, or someone trying to solo mine with our old doged protocol (60016) from back in 2014, however nothing was harmed and no coins lost. All they can do is create orphan blocks, it doesn't pose a risk to us or our blockchain. orphan blocks are completely normal, we just dont normally see that many in a row. Keep in mind pausing a wallet is something that exchanges do as preventative measure, to ensure the safety of their customers. Please don't get mad at Bittrex for being concerned about the users coins! If i ran an exchange, I would also pause the wallet until i could figure out what was happening, and why.