Just when you thought it was safe to go back into the water

I know, I can't believe it either - but the MacBook has once again broken down! Same problem as last time 'Random Shutdowns'. I rang Apple Support. They said that I need to bring it to a repair centre in Belfast. I told them that wasn't good enough and asked to speak to customer relations. After going through the same story again, (about having the logic board replaced in Switzerland and being without the machine for 5 weeks) the guy agreed to organise a courier to collect the unit from home.
I requested a replacement unit stating that the product was not fit for the purpose but they replied with a statement that it was company policy only to replace the unit after three repairs. Oh right very funny! By that time they know and I know that the 12 month warranty will have expired and then I will no longer be entitled to a replacement. This is so annoying and frankly just not good enough! Come on Apple, your customers deserve better than this.
The last guy I spoke to on the phone was able to tell me that Apple now know what the problem is and that they didn't really know back then when they replaced my Logic Board.
He tells me now that there is a heat sink on the processor which is expanding when it heats up and as it expands it is pulling on some of the contacts and causing them to disconnect. (Some are suggesting that the heat sink expands and makes contact with the metal casing and causes a short.) Now that theyhave worked this out, they are simply replacing the heat sink and not the Logic Board. I am told that this is a simple repair and that the part is readily available. Now I am waiting for the courier to arrange a pick-up. So here's hoping for a quick turnaround.

Below are two posts which shed some light on this issue http://www.macworld.com/news/2006/10/20/macbook/index.php
http://discussions.apple.com/thread.jspa?messageID=3232501
http://www.macbookrandomshutdown.com/