i cant log into my computer now

Thanks for taking the time to contact us however your issue seems more like a support question than a bug report and subsequently I am converting this to a question. In the event that you discover that is an actually bug feel free to reopen the bug report.

To discover your user and restore the password you can:

Start the pc the when you see the GRUB row...

Press ESC.

Press "e" for edit.

Highlight the line that begins kernel ………, and press "e"

Go to the very end of the line, add rw init=/bin/bash

press enter, then press "b" to boot your system.

Your system will boot up to a passwordless root shell.

Type in grep -i 1000 /etc/passwd

The system must show a row with your user name at the start of the row
for example:
danilo:x:1000:1000:ubuntu,,,:/home/danilo:/bin/bash

Here my user is danilo

Then to change your user password type in passwd username
change username with your real user

Set your password.

Type in reboot

Hope this helps

Just a small addendum. A default install will have at least 3 lines at the grub menu. One for a standard boot, one for recovery and then memtest (you might need to hit escape to see these options depending how the system is set up). The recovery option will boot to a root shell where you can follow marcobra's directions.