password not working after updates

[dmwdrown]

After installing the latest upgrade for maverick meercat and restarting the computer I can not log in. I type in my password it acts like it is going to load the screen goes black and then takes me back to the log in screen! Any ideas? It will not let me create a new user account either so I have no idea what is going on or how to fix it. I have only been using ubuntu for a few months and I am definately not tech savvy so please please please help me!?
Thank you so much!