Due to the seriousness of the issue, we have diverted dev attention back to the wallet. We are currently testing a new version, the source is available on the git. All issues have been attributed to a set of rouge nodes that are broadcasting malicious blockdata. This could be intentional, as someone tries to force PoW or zombie nodes that maintain old versions and have -setgenerate true.
Either way we are currently trying to build up nodes that have the correct blockchain, as you all know the Block explorer is one of them. If you use linux or build your own clients from source, you can do so immediately.Windows wallet that blocks bad clients will be available shortly.
repost