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

[Magicloud Magiclouds]

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.
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