GHC 6.10.0.20081007 hangs instead of giving error about missing type class constraint

The following code hangs GHC 6.10.0.20081007 on Windows

{-# OPTIONS_GHC -XFunctionalDependencies -XMultiParamTypeClasses #-}


class VectorSpace v s | v -> s where
    (*^)    :: s -> v -> v
    (^/)    :: v -> s -> v
    v ^/ s = v *^ (1/s)

it should give an error instead (1/s implies a constraint on s which I did not give)