Canon 5D2 / 5d Mark 2 Error 20

Back in 2009 I posted about the error 20 that I had experienced on my Canon 5D2

Since then I have taken the camera to be checked by my local camera specialist, Miles Whitehead, who arranged for the error codes to be checked and cleared. Since the codes were cleared from memory the error 20 message has not reappeared in around 6 months so I'm hoping that this is now resolved.