Installer closes on it's own, randomly. I tried burning new ISO Image to USB stick, but same problem.
Does anyone know the solution?
P.S. I disconnected my LAN cable and turned Wi-Fi to off, because other people said that it could solve the problem, mine didn't.
The problem seems to be due a graphics related problem in Ubuntu. You should try to boot into the "Safe Graphics" mode by selecting that option in the GRUB menu (where you select Try/Install Ubuntu when the computer starts the boot process).
Once booted with Safe Graphics mode, the problem of the installer crashing does not occur.
Here is another answer with more details: What is safe graphics mode?