Comment 3 for bug 578849

Downloaded the latest amd64 iso image and did a new install about 3 weeks ago. Update regularly, typically every day. About 1 week ago, this error appeared at boot. Rebooted, error went away. Three days ago, it came back to stay. There is a small difference at the end: instead of "unknown-block (0,0)" I get "unknown wn-block (0,0)".
Used a live cd to boot and reinstall grub. Worked fine for a day. Today the error is back. Machine boots into windoze 7 without a hiccup.