If you're using cabal to install applications from hackage, it gets a bit hairy. But if you just want to resolve your dependencies

    mkdir project
    cabal sandbox init
    cabal install dependency
    cabal repl # for a ghci instance inside the sandbox

Recommended is still to generate a .cabal file and specify your dependencies there.

Use the new sandboxing feature of cabal: http://coldwa.st/e/blog/2013-08-20-Cabal-sandbox.html

Take a look at this [1], particularly the second answer, which links to a Github Gist for "ghc-pkg-clean." I tend to use that when I run into trouble.

[1] http://stackoverflow.com/questions/7961604/fixing-issues-not...

Try checking the version of ghc you have installed.