panic! (the `impossible' happened, GHC version 6.2)

Prelude> :set -package wx
Loading package haskell98 ... linking ... done.
Loading package lang ... linking ... done.
Loading package concurrent ... linking ... done.
Loading package QuickCheck ... linking ... done.
Loading package util ... linking ... done.
Loading package data ... linking ... done.
Loading package wxcore ... linking ...
C:\Prog\ghc\wxhaskell-0.4\bin\..\lib/wxcore.o: unknown symbol `_GHCziShow_toLowe
r_closure'
ghc.exe: panic! (the `impossible' happened, GHC version 6.2):
        can't load package `wxcore'

Please report it as a compiler bug to glasgow-haskell-bugs@xxxxxxxxxxx,
or http://sourceforge.net/projects/ghc/.