CommonBackend: The md5 of the metalink does match

I am new in Linux and I am trying to install Ubuntu 12. 04 on my pc. After downloading and "burning" it on USB I try to install it. But there seems to be an error on the installation. "Could not retrieve the required installation files". It also tells me to check another file. This file writes something like this:

ERROR  CommonBackend: The md5 of the metalink does match
ERROR  CommonBackend: Cannot authenticate the metalink file, it might be corrupt


After that there is also another error which says:

ERROR  CommonBackend: Invalid md5 for ISO C:\ubuntu\install\installation.iso (14ad92270218a8925d802b3d3b6e140f != 6c086700fd56a27a09b5de552ae054fd)


Any here? What seems to be the problem?

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Same thing when I try to install earlier version 10.04 from USB. –  Michael Feb 15 at 21:15
Exactly at what moment of the installation it shows this? –  Braiam Feb 15 at 22:08
At the end. Just before finishing. I should say that I try to install Linux from wubi while on windows. I do not restart and change bios settings to run from USB –  Michael Feb 15 at 22:15
Have you downloaded again and burned another disk? That's the only issue I find. –  Braiam Feb 15 at 22:29
I have tried ubuntu 10 , 12, 13 on USB and DVDs. I cannot find the problem.Do I do something wrong? –  Michael Feb 15 at 22:32