While booting, I am getting the error message internal error: the second sector of Stage 2 is unknown." This is under Ubuntu 10.04 Lucid Lynx. After posting, the full text of the GRUB loading screen is:
GRUB Loading stage1.5 GRUB loading, please wait.... internal error: the second sector of Stage 2 is unknown.
This is an existing install that has been working for a long time. I came home to find the computer powered but not responding with no input to the monitor. Upon rebooting, this error message was displayed.