I update my GHC to 8.0.1 and failed to install any packages since then.

If I use cabal, I got 'installed package info from too old version of Cabal (key field does not match id field)' for every package.

If I use Setup.hs, I got 'Configuring Cabal-1.24.0.0...

Setup.hs: ghc-pkg dump failed'.

What should I do? Googling did not get me an answer.