Currently I have Ubuntu 11.10 as an OS and I want Ubuntu 12.04 LTS. I made a bootable USB stick with the program Startup disk creator. Everything went well (I chose the language, and then I chose 'Install'), the purple screen with the title 'Ubuntu' came up and it started loading too.
After some time black screen came up with white letters. Last sentence was something like:
Panic occurred, switching back to text.
I tried it several times, the same thing happens. I tried clicking on Try Ubuntu from USB too but it didn't work either.