Am 05.01.2011 09:24, schrieb Magicloud Magiclouds:

Hi,
  I am using Data.Binary which defined "instance Binary a => Binary
[a]". Now I need to define "instance Binary [String]" to make
something special for string list.
  How to make it work? I looked into the chapter of
overlappinginstances, nothing works.

Just a guess: Have you enabled TypeSynonymInstances? (As String is a type synonym, at least this extension would be required)