Downloaded the Ubuntu 12.04 ISO? Failed to boot from it with this error? Checked the hash of the ISO and it seems correct? Thoroughly confused? grkrishna1984 is your man. Whilst I was sceptical at first, his advice proved good. There is indeed a file called “ubuntu” in the root of the ISO, and removing it seems to solve the problem.
The ISO Master program he refers to is available on Linux and Windows. Simply use it to open up the ISO file, and remove the offending file:
Then File > Save As and burn to CD.