As far as I'm aware 11.10 doesn't contain the package "libgtksourceview1.0-0" in the repository by default so to fix the RC we need to add a repository that does contain the package. The easiest way to fix this is by adding the Universe repository for Natty (11.04).
In a Terminal session enter:
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sudo add-apt-repository 'deb http://archive.ubuntu.com/ubuntu/ natty universe'
sudo apt-get update
sudo apt-get install libgtksourceview1.0-0