I have Ubuntu 12.04 64bits and it worked fine until today. This is the problem: when I introduce my password at the login screen a black window appears and then it comes back to the same screen. If I start as a guest everything works fine, but I can't log in with my normal account.
I tried the following with no luck:
I can login through a virtual terminal (ctrl+alt+F1) without a problem.
Thanks in advance.