I'm trying to install the mtl package with the current HEAD version of Haskell, and I get the following error message:

Control/Monad/Error.hs:76:10: Duplicate instance declarations: instance Error e => Monad (Either e) -- Defined at Control/Monad/Error.hs:76:10-38 instance Monad (Either e) -- Defined in Control.Monad.Instances

Control/Monad/Error.hs:87:10: Duplicate instance declarations: instance Error e => MonadFix (Either e) -- Defined at Control/Monad/Error.hs:87:10-41 instance MonadFix (Either e) -- Defined in Control.Monad.Fix cabal: Error: some packages failed to install: mtl-1.1.0.2 failed during the building phase. The exception was: ExitFailure 1

The library installs fine with earlier versions of Haskell. Is there something wrong with my installation, or is this a new incompatibility? If the latter, is a corrected version of the mtl library going to be available soon? Alternatively, how can I fix it? Kathleen