[Haskell-cafe] Cannot install any packages after upgrading to GHC 8.0.1

Hi, 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.