<command line>: cannot satisfy -package-id mtl-2.0.1.0-5b7a9cce5565d8cc8721ba4f95becf1b
(use -v for more information)
However, cabal list tells me:
* mtl
Synopsis: Monad classes, using functional dependencies
Default available version: 2.0.1.0
Installed versions: 2.0.1.0
License: BSD3
The right version, but possibly not the right ABI hash. Also, it might be broken by some other dependency; try "ghc-pkg list" which should give you an idea about both issues. ghc is regrettably not very good about saying *why* it "cannot satisfy" a package dependency.