I have a problem that i never seen before. I upgraded my Ubuntu 12.04 64bit to 14.04 using the following command:

```
$ sudo update-manager -d

```

After that I can't login to my user account, when I log it just flashes and then it goes back to the login screen, but the odd thing is that I can log in with the guest account.

I tried to create another account but couldn't log to that account either.

FYI I don't have any graphic cards like NVIDIA or AMD.