Here's a list of what I tired so you know what I did:
Installed the driver from the hardware additional drivers, update manager added another driver this hosed the video completely. I formated, re-installed and tried
for text mode which gave me a clue on what the problem was.
sudo sed -i -e 's/#GRUB_TERMINAL/GRUB_TERMINAL/g' /etc/default/grub
Read and tried the fixes on https://bugs.launchpad.net/ubuntu/+s...b2/+bug/699802
Tried in grub NOMODESET. Lastly I tried Commented #Grub_Hidden_Timeout
After all that, I finally got it! I've been beating this thing to death, with searching and experimenting. But here's the answer. If you have a Nvidia video card (mine is a Nvidia GeForce 7025 / nForce 630a).
I kept getting Not optimum mode : Recommended mode 1280X1024 /60.
When I commented out grub so I could see the boot sequence I founderror: no video mode activated.
So when in grub I noticed GRUB_GFXMODE= commented out, so I uncommented it and added the correct video specs of 1280X1024 to it. Saved it and rebooted and low and behold it works.
Here's the break down:
Open the terminal and paste this in:
hit enter, enter your password, and about 10 lines up from the bottom you'll see
gksudo gedit /etc/default/grub
You need to edit two parts, first remove the # from the line, then change the 640X480 to the video card specs, example: mine is 1280X1024.
Save the file and run and reboot. Both errors went away after I did this. I hope it works for you as well.