2012/10/13 Ramana Kumar
I'm not sure why that error happened but it happened to me too.
The problem seems to be that those files were not part of any package, but now are in ghc.
I removed the offending files manually and tried again, and ran into more problems (although everything installed, there were many warnings about interface files being the wrong version and being skipped). So I'm not sure what the correct way out is. Perhaps it will require some manual removals then reinstalls.
This is a problem with ghc-pkg version. For previous version of ghc I had to do: $ pacman -Rcs ghc then reinstall ghc and needed haskell-* packages. I think you'll want to remove the offending files before installing ghc again. I hope this solve the problem. Fabio
