frequency out of range - please change display mode

I usually get this problem every time i upgrade OS.What normally happens for me is after displaying out of frequency range for a while it eventually loads ubuntu without problem. it was the grub menu loaded before ubuntu that was replaced/not shown because of the out of frequency warning.For some, if ubuntu still doesn't load,by pressing enter whilst seeing out of frequency range you should get ubuntu to boot.

For me it was a simple fix .

Once in Ubuntu go to a terminal and run:

gksu gedit /etc/default/grub

A graphical text editor will open. Remove the # from in front of:

GRUB_GFXMODE=640x480 

Save the file and close it. Now run:

sudo update-grub

Reboot, and the "frequency out of range" issue should be resolved.