Message appears saying that an application needs the default keyring password in order to run but I didn’t enable or enter a password for the keyring
This is more true in case you are using Ubuntu One online sync. The remedy provided is that you simply delete the login keyring.
Step-1: Ubuntu main menu -> Applications -> Accessories -> Passwords and Encryption Keys
Step-2: In Passwords tab, right click Passwords: login. In the menu select Delete … option.
Actually this demand is from UbuntuOne sync daemon. This may not work in Precise Pangolin.