You can found this message trying to boot from a recent computer, if is your case you should try to append the boot parameter mem=1952M or other values to the boot parameters (pressing TAB key in the first boot menu)

This parameters tells the kernel how much memory your computer has, sometimes the BIOS don’t give the correct information and so you need to assign it.

Note: this option doesn’t always works magically and you need to play with different values, like 1024M (even if you have 4G), 512M, 2G, etc…