Following the last couple of Ubuntu installs (Ibex, Jaunty), logging in has occasionally presented me with a message along the lines of "Your $HOME/.dmrc file has incorrect permissions and is being ignored blah blah blah". It's easy to fix if you run the following in a terminal window.

sudo chmod 644 ~/.dmrc
sudo chown $(logname) ~/.dmrc
sudo chmod -R 700 ~/
sudo chown -R $(logname) ~/

This simply updates the ownership of the home folder to the currently logged in user, then makes sure that .dmrc has the correct permissions.