MacBook pro Yosemite - unable to dualboot with Ubuntu 14.04

Hi,

I have followed these steps in order to dual boot my MacBook (OS X Yosemite 10.10.5, 2.9GHz Intel i7) with Linux Ubuntu 14.04:

http://www.howtogeek.com/187410/how-to-install-and-dual-boot-linux-on-a-mac/

When the process of burning the Ubuntu 14.04 version (both 32-bit and 64-bit) has completed I get the following error message:

"The disk you inserted was not readable by this computer."

If I then boot from this disk all that appears on the screen is a blinking cursor. I have burned the disk using Disk Utilities at slowest speed of 2x and other speeds too. I've tried burning both 32-bit and 64-bit versions and used a 32-bit disk that I successfully dual-booted a windows system with the same unsuccessful outcome.

I have burned both 32-bit and 64-bit versions using Disk Utilities and Toast Titanium but I am still experiencing the same error.

Prior to booting from the Ubuntu disk I also partitioned my hard-drive to make room for Ubuntu.

Please help on this issue as I really need to get Ubuntu running on this system.