First add the svn ppa:
sudo add-apt-repository ppa:team-xbmc-svn/ppa
Next fetch the essential build tools and all of XBMC's required libraries and headers:
sudo apt-get update
sudo apt-get install build-essential
sudo apt-get build-dep xbmc
The next step is to get the latest source code for the most recent svn. To do this subversion must be installed, and can be done so by running:
sudo apt-get install subversion
Then checkout the latest svn source code by executing:
cd $HOME
svn co https://xbmc.svn.sourceforge.net/svnroot/xbmc/trunk/ xbmc
The above command will place a copy of the source code in a directory named "xbmc" in the home directory.
Within the xbmc directory that the source code is contained, run the following commands in order to compile it:
./bootstrap
./configure --enable-vdpau --disable-pulse --disable-crystalhd
make -j2
make -C lib/addons/script.module.pil
make -C lib/addons/script.module.pysqlite
sudo make install
Replace the number 2 with the number of cores in your processor.
Now make a backup of the original XBMC install, and make the recently compiled version the default one to boot.
sudo mv /usr/bin/xbmc /usr/bin/xbmc.bak
sudo mv /usr/bin/xbmc-standalone /usr/bin/xbmc-standalone.bak
sudo ln -s /usr/local/bin/xbmc /usr/bin/xbmc
sudo ln -s /usr/local/bin/xbmc-standalone /usr/bin/xbmc-standalone
Almost done, reboot:
sudo reboot
Reinstall nVidia Drivers:
sudo apt-get install --reinstall nvidia-current nvidia-current-modaliases nvidia-settings