See the announcement on the GHC Developer’s Blog for details.
Unfortunately due to a mix-up in the release process I’ve had to recall the binary distributions of this release. I’ve pulled down the binary distributions for the moment; they will be back in a few hours.
While we typically try hard to avoid changing artifacts after they are announced, given how quickly this issue was caught we thought this was the least bad option. Again, my apologies for the confusion and thanks for the patience.