can't enter password

[wg5o]

I upgraded 32 bit Ubuntu 10.04 to 12.04. When I click on my name at log in it gives me no chance to enter my password, it just says "log in." If I click on "avg," (whatever that is) it says "Password," and allows me to enter mine, which is rejected. I can log in as "Guest," and the installation seems otherwise good. If, as a guest, I go to system settings, system, user accounts, my password is accepted, and I have tried Automatic LO in both on and off, without effect.

I need to find a way to log in, or how to go back o 10.04.

Help!

Andy Pickens
San Antonio, TX

wg5o@sbcglobal.net