I attempted to install the SCROT screenshot tool. I type startx as the instructions suggest. After this, I cannot log into the Pi desktop anymore. Upon entering the password, the screen goes black, the comes right back to the login screen. I have a monitor and keyboard attached to the Pi directly.
The password is correct as I can successfully login with Pi username using Putty.
I can see my screen saver in the background behind the login box.
While I don't know what caused the problem, you can fix it by doing the following from the command prompt:
cd
This will change to your home directory (assuming the default Raspbian install - this will be /home/pi)
next rename the .Xauthority file:
mv .Xauthority .Xauthority.backup
reboot your Pi
sudo reboot
then startx as normal:
startx
If x starts successfully you can remove the .Xauthority.backup file:
rm ~/.Xauthority.backup
This Raspberry Pi Foundation forum thread contains some further details.
