Problem with guest account

Never tried it before so I was trying to see what it did so I can let someone use my MBP for web browsing because that's person's PC is on the fritz. However, I wanted to see if maybe I could try the guest account because when I've lent it out before I've ended up with Safari folders modified (once even deleted) and my desktop folders shuffled around.

So I entered the guest account. I did open a folder and got into Applications to start Firefox and even create an alias. However, I've never done this before so I tried logging out. I got something about the keychain being deleted (I canceled) and then I got a black screen with an arrow cursor. After a minute I just powered down with the power button and powered on again. I could get into my normal administrator account, so I logged out and got into the guest account again. When I tried logging out I got the black screen again, but no message about the keychain.

Anyone know what's going on?

It's a mid-2012 non-Retina with an SSD, if that helps.