Please help Update pack 6 LOCKED me out!

[Pa773rnR3c0gn1710n]

I just updated my LMDE from update pack version 4 to 6.

After the update finished things looked ok but I noticed that my terminal was solid black with no command prompt. Then I rebooted and got the sign in window with my user name but it won't accept my password (gives me an 'Authentification failure' message)

I've tried simply entering 'mint' as the user and no password due to some problems people over sat the xfce forum had but no luck.

I can of course access my files via a live USB distro. Is there a config type file which I can edit which might have gotten damaged somehow during the upgrade? This is all rather perplexing and is a pretty severe fail.

Thanks anyone who can help.

[Pa773rnR3c0gn1710n]

Update: I ended up installing Maya. This experience has totally freaked me out re LMDE