If I'd posted this yesterday, you wouldn't have believed me that my beloved Mac has played April Fool's day on me and has stopped working yesterday. I've spent the whole evening and most of today diagnosing the problem. It has turned out that problem is around disk controller so the Mac had to go into Apple's care. Fortunately, it's quite easy to transfer the whole personality of a computer by moving the disk to another computer (Hvala SkIn!)
I'm obsessed with backups, so I had a pretty recent backup from which I could restore my system. Let this post serve as a wake call for you to make a backup now. Even more so since Saturday was World Backup Day!