I installed 11.10 on my desktop PC but get a black screen after the BIOS screen when I try to boot it. I was able to run 10.04.04 on my hard drive before installing 11.10 and I am also able to use 11.10 on my usb pendrive and CD ROM. I've tried unplugging all USB devices before booting and also upgrading from 11.10 to 11.10. Holding the shift key from the BIOS screen doesn't allow me to access the GRUB menu to try:

Highlight the first entry, press “e” to edit it. Navigate to words “quiet splash”, delete them and type “nomodeset” in their place (without quotes). Press Ctrl + X to continue boot. Once on the desktop, go to System > Administration > Additional Drivers and activate the recommended drivers.

So running 11.10 on my pendrive, I tried editing /etc/default/grub, commenting out the GRUB_HIDDEN_TIMEOUT setting by putting a '#' in front of it to display the grub menu and setting GRUB_TIMEOUT setting to a value greater than or equal to 1 e.g. GRUB_TIMEOUT=10.

However, when I run sudo update-grub, I get:

/usr/sbin/grub-probe: error: cannot find a device for / (is /dev mounted?)

I get the same error with update-grub after:

sudo mount /dev/sda1 /mnt

and after:

sudo grub-install --root-directory=/mnt /dev/sda
reboot
sudo update-grub

Other suggestions to fix the update-grub problem:

Open synaptic, then purge all the related grub installed packages and reinstall grub-pc then and finally: sudo update-grub

Or use Grub Customizer http://ubuntuforums.org/showthread.php?t=1195275

What would be the best way to approach this? I'm concerned about purging "all the related grub installed packages" but if it's true some files are corrupted this would seem necessary. Also, was I executing the correct commands i.e. with mount and grub-install, before running grub-update?