While the Dev and Beta channels are still stuck in version 4.0, Chromium for Linux Daily builds make it to version 5.0. The Daily PPA is updated more frequently than the Dev PPA, but it is completely untested, that certainly makes it more unstable and unreliable. It works and loads web pages quickly too.
Remove your current Chromium build and use the codes below if you want a risky cutting-edge Chromium 5.0 with no damned new features in your Ubuntu ‘Karmic’
sudo apt-repository ppa:chromium-daily/ppa
sudo apt-get install chromium-browser