MemTest is returning large numbers of errors in Test 7, no matter what ram I use

This is a known bug with the Memtest86+ v4.20 distributed with several Linux distributions, caused by a change in the compiler (gcc) used to compile Memtest86+. Unfortunately, this means that the Memtest86+ included on the Ubuntu 12.10 (Quantal) ISO contains this bug.

A fixed Memtest86+ for Quantal should soon be available through the repository. In the meantime, you can add a non-bugged Memtest86+ v4.20 to your GRUB boot selection via the following commands (this assumes that you have Ubuntu installed):

sudo apt-get install grub-imageboot
sudo mkdir -p /boot/images/
wget http://www.memtest.org/download/4.20/memtest86+-4.20.iso.gz -O - | \
gunzip | \
sudo tee /boot/images/memtest86+-4.20.iso > /dev/null
sudo update-grub2

This will download Memtest86+ from the official website and include it in GRUB through the grub-imageboot utility. Once you reboot, you will find the new option Bootable ISO Image: memtest86+-4.20 in GRUB.