all pools are coming back online. about 4 of them went offline.
there is no "bug". what happened here can happen to bitcoin.
when the difficulty dropped, a few people jumped onto the network with several petahash. they did this until the difficulty increased too much for them to mine blocks in a profitable manner. the difficulty, the same as bitcoin, increased 4 fold as this was happening.
we are looking into shortening the retarget now.