I've had Ubuntu as the sole OS on my desktop for a couple years. Updated it to Precise soon after it came out. Today I decided to try dual booting to Windows 8. I bought a new, separate hard drive (SATA) to install Windows on. My Ubuntu installation is on my older PATA disk.
I disconnected the Ubuntu drive completely when installing Windows. It seemed to go OK.
I've now re-attached the disk with Ubuntu on it. I was able to boot to Ubuntu, run update-grub, and see that it recognized Windows 8. I now have a Windows 8 option in grub on startup.
However, when I select that option I get a couple seconds of the Windows boot screen, followed by a very brief flash of a "Your PC needs to restart" error message (see http://i.stack.imgur.com/eNzTk.jpg), and then the computer spontaneously reboots, and I end up back at the grub screen.
I'm not sure what to try next. Is this a windows security measure to prevent the OS from being loaded by some malicious bootloader? Is the mysterious "uefi" somehow to blame? Have I missed something obvious?
EDIT: This seems to be the same problem as Dual-boot Windows 8 and Ubuntu, separate HDD, Win8 boot failure from GRUB, but the accepted answer there is to buy a $25 copy of EasyBCD and boot from Windows. :(