[Haskell-beginners] cabal install happstack

[Gary Klindt]

Hey Haskellers,

I tried to install happstack. Unfortunately I get the following error:
 > cabal install happstack
-Resolving dependencies...
-cabal: cannot configure deepseq-1.1.0.0. It requires containers >=0.2 
&& <0.4
-For the dependency on containers >=0.2 && <0.4 there are these packages:
-containers-0.2.0.0, containers-0.2.0.1 and containers-0.3.0.0. However 
none of them are available.
-containers-0.2.0.0 was excluded because containers-0.4.1.0 was selected 
instead
-containers-0.2.0.1 was excluded because containers-0.4.1.0 was selected 
instead
-containers-0.3.0.0 was excluded because containers-0.4.1.0 was selected 
instead

I wanted to deselect containers:
 > ghc-pkg unregister containers-0.4.1.0
-ghc-pkg: unregistering containers-0.4.1.0 would break the following 
packages: Cabal-1.10.2.0 (use --force to override)

But I did not want to use the force option, because I like cabal, and 
don't want to break it.

What should I do?
 > ghc --version
-6.12.1

Greets
Gary