I'm trying to install Ubuntu 12.04 using live USB but getting error message that my CD or DVD drive lens is needed to be clean or I have burnt CD at higher speed. Why I'm facing this problem as I'm using a Live USB, How can I get through it. I want to install it on my hard disk.
You'll have to check you memory using a memtest. Also, check the .iso image using instructions here: https://help.ubuntu.com/community/HowToMD5SUM