[Haskell-beginners] can't install hackage package

Hello, I've been using this hackage package "rex" without problems on two computers (linux, windows) but now I fail setting it up on a third computer which confuses me, and the error message is not really enlightening for me: $ cabal update Downloading the latest package list from hackage.haskell.org $ cabal --version cabal-install version 1.16.0.2 using version 1.16.0.3 of the Cabal library $ cabal install rex Resolving dependencies... cabal: Could not resolve dependencies: trying: rex-0.3.1 Any idea? Thank you! Emmanuel