produce better error message when presented with an unknown type to load
produce better error message when presented with an unknown type to load

darcs-hash:20060718014556-1a7c6-17f637a8a5271815f99ce17856796aaff28ea629

kirbyfan64/jhc,kirbyfan64/jhc,kirbyfan64/jhc,kirbyfan64/jhc