Macbook Pro was running fine this evening then locked up tight as I was browsing. I power-cycled it. I got to the Apple-and-spinning-thing screen and no further. I rebooted in 'verbose' mode. The machine produced some text as per normal. Once it displayed "parent ready after 1 tries" it stopped. After 5-10 seconds, the machine powered off. I've done this a few times now :-/ Any ideas?