Install Ubuntu in UEFI mode (unable to boot from USB)

I recently bought a Dell Inspiron 15R SE with Windows 8 (64 bit) pre-installed (UEFI supported). I want to install Ubuntu in dual boot with Windows 8. I tried to follow all these instruction and these instructions too.

• So, I set Secure Boot to "off" into BIOS and I disable Fast Startup as described here.




• I created a bootable USB key for Ubuntu (Ubuntu 13.10 64bits international Edition) with Unetbootin.

The problem is I am unable to boot from the USB key. The computer tries to boot into infinite loop (when the USB key is plugged in, the computer starts and the Dell logo appears. The little blue progress bar is growing normally. When it is complete, the computer restarts and does the same thing).
I also tried to boot from USB with "Legacy Boot" option instead of UEFI. In this case, the computer freezes at Dell logo.

Of course, I tried to boot from my USB key on an other computer having normal BIOS and it works perfectly.

Have you ideas about what I need to do to be able to boot from USB?

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UPDATE:

What I have tried:

• With UEFI Boot mode:

  
  
  
  
  
  • Secure option: Disabled
  
  
  • "Intel speed step": Disabled
  
  
  • Windows 8 FastStartup: Disabled
  
  
  
  
  
  

  Using bootable USB key for Ubuntu (Ubuntu 13.10 64bits international Edition) with either Unetbootin or Linux dd utility.

  
  
  

  Result : Unable to boot from the USB key. The computer tries to boot into infinite loop.

  
  
  
  
  
  • With "Legacy Boot" option:
  
  
  
  
  
  

  Using bootable USB key for Ubuntu (Ubuntu 13.10 64bits international Edition) with either Unetbootin or Linux dd utility.

  
  
  

  Result: Unable to boot from the USB key. The computer freezes at Dell logo.
  If I press F12, the computer freezes instantaneously.