ghci can't find Paths_ module created by cabal

I'm trying to run cabal-install in ghci so I can run it under the ghci debugger. However I try it, though, I always get one of these two errors: /src/greenrd/darcs/cabal-install/Main.hs:70:17: Could not find module `Paths_cabal_install': Use -v to see a list of the files searched for. Failed, modules loaded: none. or <command line>: Could not find module `Main': Use -v to see a list of the files searched for. -- Robin