Help! I can not access my computer!

Hi, I am stuck trying to log in. I get the login window, where you can choose a user, but then I can not select a user with the mouse. I have tried selecting one, just scrolling down. I get the password window pop up, but when I type in the password, I am sent back to the login, choose user, window! What is happening?

The last thing I did was accept some updates, but didn't even look at what they were :-(

Anyone can help?

Thank you,

J1jl