[Haskell] haddock not finding base lib docs -- $topdir ?

I'm running haddock for the first time, via cabal. I get the following message when i do "runhaskell Setup.hs haddock" on monadLib: Warning: cannot use package base-2.0: HTML directory $topdir\html\libraries\base does not exist. I do have c:/ghc/ghc-6.6/doc/html/libraries/base/. Is there some way i can let cabal know how to find it? What is $topdir about? Thanks, - Conal