I have run into a really strange disk error. Running Windows 7 Ultimate 64bit, the system freezes once every second week and I can't do anything but restarting the computer with HW reset. After this, boot fails with disk read error. If I reboot the system with Seagate diagnostic SW I can run all tests without problem. Still I can't boot. If I move the disk to another system, I can read the drive and files without any problem. And now comes the real strange thing: After reinstalling the drive in the original computer everything is fine again! I have to move the disk to another computer to make it work. I have tried to just unplug the disk and put it back again without moving it to the other computer in between, but that trick does not help. Extremely strange. Syslog does not provide any help either. It's a 1Tbyte Seagate SATA drive.
I had a similar problem a while back.
Turned out my SATA controller was dying. Now it's completely dead and won't recognize any drives. I plugged in a SATA controller card and the computer is up and running again (had to reinstall everything though).