I have been bitten by the bug described in Microsoft's KB3033929.
What I did to fix it:
- Dug around and found my Windows 7 install disc. Luckily I had one. Woe be to you if your computer came without one.
- Started my computer with the Windows 7 install in the CD drive. Did the obvious things until I got to a dialog that gave me the option to Repair your computer--which I selected.
- In the following window, I selected Command Prompt and ran
- That seemed too easy, so I also ran the option to check for and correct startup issues.
- Removed the Windows 7 install disc media After the automatic reboot (into Windows--bye, bye GRUB), then manually rebooted.
- Prompted windows to try (again!) to install the offending update.
- Rebooted to confirm that the update took.
- Reinstalled GRUB using Rescatux.