Unable to log back in

Hey!

I installed Kali Linux on VirtualBox. Worked like a charm, logged in, installed some software with sudo..using my password. Then I left the computer for an hour, and when I got back I had to log back in..and my password didn't work. There is only root user on the installation, and I know the password is correct because I used it as sudo. Anyone else had this problem, or know what might'v caused it? I'm considering installing Kali instead of Ubuntu on this laptop, but not if it's gonna lock me out :(

have you tried without sudo?

I might'v been unclear. It's when I try to log back in, that it sais that my password is incorrect!

... I at this point would re-install the image

Yea, it's gone. I just wanted to make sure this isn't a common issue before I install it on a laptop. I hate having to reinstall because I was locked out :(