Error: invalid environment block. Press any key to continue...
The error message appears immediately after the boot screen on purple background. Ubuntu 12.04.1 LTS.
Press E at the GRUB menu. Find the line saying
Run the following command, and then when it asks for your password, type it, and press Enter. Your password will not be shown, not even asterisks.
Then, run each command, one-by-one.
The second-to-last command should show