login problem in ubuntu 11.04

[Shashwat]

I am using ubuntu 11.04 along with windows xp sp3 as a program in it. It was working fine, but now I cant login in to ubuntu. At the login screen it is showing a message, "Install problem. The configuration defaults for GNOME Power manager have not been installed correctly. Please contact your computer administrator."
It is not the default login screen. It is asking me for username and password, but when I enter the same it reappears again. please suggest me what to do or I should install ubuntu again?

 

[nims11]

you may press ctrl+Alt+F1 when the login screen appears to get into command line and do the troubleshooting.
or you may boot into the recovery/failsafe mode from the grub boot menu and start the basic VGA GUI.

then from terminal try one of the following. after performing any of the below, reboot and check. if its working, well and good, else try other methods.
1. reinstall gdm by sudo apt-get install gdm
or
2. try installing kdm by sudo apt-get install kdm. after installing, type sudo nano /etc/rc.conf and at the end of the file, add kdm inside the DAEMONS=()
or
3. reinstall GNOME by sudo apt-get install gnome-desktop
or
4. reply if the above steps don't work.