Hi. Sorry for singling out this one message of the thread to reply to a bunch of messages.
Can you try upgrading "cabal-install" to see if the new solver handles it better? I think the new version works with what is in the platform. If you also get errors there might be ways to make it go ...
I just tried installing cabal-dev on a clean platform, and I can confirm it doesn't work: $ cabal install --dry-run cabal-dev Resolving dependencies... In order, the following would be installed: tar-0.3.2.0 (new package) transformers-0.2.2.0 (new version) mtl-2.0.1.0 (new version) parsec-3.1.3 (new version) network-2.3.1.0 (new version) HTTP-4000.2.3 (reinstall) changes: mtl-2.1.1 -> 2.0.1.0, network-2.3.0.13 -> 2.3.1.0, parsec-3.1.2 -> 3.1.3 cabal-dev-0.9.1 (new package) Warning: The following packages are likely to be broken by the reinstalls: haskell-platform-2012.2.0.0 Use --force-reinstalls if you want to install anyway. Investigating the dependencies, it seems cabal-dev depends on transformers < 0.3, which in turn leads to an older mtl being picked, and all the other problems. I've only just come to this thread. There are a couple of things that are strange. The original poster shows logs where base version changes are listed. That's really puzzling to me. GHC usually has one version of base installed, and that can't be changed. So why are there several? Also, there are multiple versions of the Haskell Platform being listed as possibly being broken. How can multiple versions of the platform be installed at once? So something to me looks to be strange with that installation. There also seems to be a misconception that "switching to cabal-dev" means no longer using cabal-install. I just want to clarify that this isn't the case. The use of cabal-dev offers additional sandboxing functionality and wraps cabal-install, but you're still using it. The next release of cabal-install (don't know when that'll happen though, unfortunately) will most likely have sandboxing functionality built-in. Cheers, Andres