I've been using Mint KDE for months and it's been excellent, no problems at all. But today I started up my laptop and found that when I try to log in, the screen flashes black and I get the log in screen again. If I deliberately use the wrong password, it tells me so without the screen flashing black. The black screen thing only happens when I use a correct log in.
So I tried switching to console login. When I use a correct log in there I get, '-bash.... error loading shared library libtinfo.so.5'. And then it asks me to log in again

Even if I start up in recovery mode and use root login I get the same problem.
Is there a way with a live USB that I can fix whatever is causing this? Or maybe I can edit something in the grub option so I can log in as root? If I can just get past the login screen that would be a good start

Thanks for your help