Really sorry - can't seem to find it right now... will keep looking and repost if I do find it.
The other thread was saying something about someone who had their phone in an airconditioned appartment and had left it on the side, charging. When they came back to it, there was a crack on the inside.
I think that the general outcome of the thread was that this was a manufacturing defect and that you should push to get it repaired/replaced under warrantee and I think that you would be covered, providing you didn't drop the phone.