i can not login into my account

Thank you for taking the time to report this issue and helping to make Ubuntu better. Examining the information you have given us, this does not appear to be a bug report so we are closing it and converting it to a question in the support tracker. We appreciate the difficulties you are facing, but it would make more sense to raise problems you are having in the support tracker at https://answers.launchpad.net/ubuntu if you are uncertain if they are bugs. For help on reporting bugs, see https://help.ubuntu.com/community/ReportingBugs#When%20not%20to%20file%20a%20bug. There is also a vibrant support community available at http://askubuntu.com and you might consider asking your question there.

Ubuntu 11.10 is still in alpha, and bugs, including serious bugs, are to be expected. This may be due to a bug, and if it is, then it could be helpful to you report it, after reading https://help.ubuntu.com/community/ReportingBugs carefully.

When you say that the login "failed," what do you mean? Do you mean that it told you that your password was incorrect? Or that it produced a completely blank and unusable desktop? Or something else entirely? Does it fail only when "Ubuntu" is your session type, or only when "Ubuntu 2D" is your session type, or only when "GNOME" is your session type, or does it fail for multiple session types?

Also, if you press Ctrl+Alt+F1 to get to a virtual console, are you able to log in with your username and password? (You won't see any placeholder characters like * when typing your password in to command lines, like this, but that's OK, just type it in when asked for it and press enter.) If so, then what happens when you run these commands to update your system (you might want to connect your computer to the Internet with an Ethernet cable first, as it is somewhat cumbersome to get an Ubuntu system connected to a wireless network without a working graphical user interface)?

sudo apt-get update
sudo apt-get -y upgrade
sudo apt-get dist-upgrade

If you are able to install any updates using those commands, then try restarting ("sudo reboot" without the quotes, or Ctrl+Alt+Delete while still in the virtual console) and see if that fixed your problem using the graphical login screen.