Hmm, Now when I tried to run Leksah, I get not only some broken packages (which I can avoid for my current project), but: <command line>: cannot satisfy -package-id base-4.5.1.0-7c83b96f47f23db63c42a56351dcb917: base-4.5.1.0-7c83b96f47f23db63c42a56351dcb917 is unusable due to missing or recursive dependencies: integer-gmp-0.4.0.0-c15e185526893c3119f809251aac8c5b (use -v for more information) So I tried to install base, then re-install it, but both fail; Any hints? ------------------------------- C:\Users\guthrie>cabal install base Resolving dependencies... All the requested packages are already installed: base-4.5.1.0 Use --reinstall if you want to reinstall anyway. C:\Users\guthrie>cabal install --reinstall base Resolving dependencies... cabal: Could not resolve dependencies: next goal: base (user goal) rejecting: base-3.0.3.2 (conflict: base => base>=4.0 && <4.3) rejecting: base-3.0.3.1 (conflict: base => base>=4.0 && <4.2) rejecting: base-4.6.0.0, 4.5.1.0, 4.5.0.0, 4.4.1.0, 4.4.0.0, 4.3.1.0, 4.3.0.0, 4.2.0.2, 4.2.0.1, 4.2.0.0, 4.1.0.0, 4.0.0.0 (only already installed instances can be used) C:\Users\guthrie>ghc-pkg list base WARNING: there are broken packages. Run 'ghc-pkg check' for more details. e:/Plang/Haskell Platform\lib\package.conf.d: base-4.3.1.0 base-4.5.0.0 base-4.5.1.0 The following packages are broken, either because they have a problem listed above, or because they depend on a broken package. HTTP-4000.2.3 haskell-platform-2012.2.0.0 Can I just unregister the old Haskell platform, I now use a newer one? Ghc-pkg list : ... {haskell-platform-2012.2.0.0} haskell-platform-2012.4.0.0 haskell-src-1.0.1.4 haskell-src-1.0.1.4 haskell-src-1.0.1.5 haskell-src-1.0.1.5 (haskell2010-1.0.0.0) (haskell2010-1.1.0.1) (haskell2010-1.1.0.1) haskell98-1.1.0.1 (haskell98-2.0.0.1) (haskell98-2.0.0.1) -------------------------------------------