All was fine in 12.04, in this case I'm using virtualbox in Windows.
Last days the warning message about my Ubuntu version no longer being supported was coming up pretty often, so, yesterday I finally decided to upgrade.
The upgrading process ran ok, no errors, no warnings.
After rebooting the errors started to happen.
Just after booting up there were some errors about video, gnome, and video textures (sorry I didn't care in that moment so I don't remember well).
Luckly that went away after installing VirtualBox additions.
But the big problem here is that I can't use the terminal.
It opens Ok when pressing control+alt+t, but most of the commands cause instant closing.
For example, df, ls, mv, cd... usually work, although it has closed few times.
But 'find' causes instant close. 'apt-get' update kills it too, just after it gets the package list from the sources, when it starts processing them.
I've tried xterm, everything works and I have none of that problems.
I have tried reinstalling konsole, bash-static, bash-completion, but nothing worked.
I have no idea what to do as there is no error message to search for the cause.
It seems something related to bash, but that's all I know.