When trying to install ubuntu-12.04-desktop-amd64.iso from USB I get one of the following errors

http://en.wikipedia.org/wiki/Machine_Check_Exception states the error can occur due to

-poorly fitted heatsink/computer fans (the same problem can happen with excessive dust in the CPU fan)
-an overloaded internal or external power supply (fixable by upgrading)

So I tried the following

-Using rubbing alcohol to remove all the thermal paste from the CPU and heatsink, I then reseated the CPU after checking all the pins on the MOBO, everything seems fine.
-Boot without the GPU to see if was the PSU that is being over stressed.
-Removing all RAM apart from one stick and running a Memtest86 which it passed
-Using Ubuntu 10.04.4 Desktop 64 bit (Different USB slots and USB sticks)
-Using Ubuntu 12.04 Desktop 64 bit (Different USB slots and USB sticks)
-Reset the BIOS using the Clear CMOS jumper
-Removing all HD power cables and SATA cables
-Updating the BIOS from F2 to F6

My PC is using the following parts.

-Gigabyte GA-Z77-DS3H (F6 BIOS)
-Intel Core i7 3770K 3.5GHz Socket 1155
-G-Skill 8GB (2x4GB) DDR3 1600Mhz RipjawsX Memory Kit CL9 (9-9-9-24) 1.5V
-Be Quiet Shadow Rock Pro
-Be Quiet Pure Power 730W Modular PSU
-Sapphire HD 6870 1GB GDDR5 DVI HDMI DisplayPort PCI-E Graphics Card

Any ideas?