Note: Do not repair the MBR unless you do not want your data back. Doing so will just leave you with a encrypted drive and will not fix the problem.
I have put together a youtube video showing the ransomware in action.
When the infection is first started it will modify the MBR and then reboot the computer. On reboot it will perform a fake Chkdsk, which is actually when it is encrypting your drive.
Then it will show a lock screen with information as to what happened and a password prompt to decrypt your data. To get the password you need to pay the ransom.