I knew that you would know
For a PC to be out of action because of a motherboard, I would think less than 28 days would be inconvenient. It is something that is used everyday and is now part of our daily lives.
The board could be faulty at the time of sale in this case. If the chip was faulty at day 1, it doesn't mean it will blow on day 1, it could blow 11 months later... Just like an bubble in a car tyre - its going to blow someday
I guess the burden of proof go to the manufacturer to show that this wasn't the case... which is what is happening