In order to be able to use the latest Aurora-Sim "NoRecursion" stuffs, you have to update your mono at least > 2.6

Here are the scripts will let you do that.

Instructions (mono 2.10.2):

1.- wget --no-check-certificate https://raw.github.com/EnricoNirvana/mono-install-scripts-for-Aurora-Sim/master/install_mono-2.10.sh
2.- chmod 755 install_mono-2.10.sh
3.- ./install_mono-2.10.sh

4.- add to your .bashrc these lines at the top : 

export PATH="/opt/mono-2.10/bin:$PATH"
export PKG_CONFIG_PATH="/opt/mono-2.10/lib/pkgconfig:$PKG_CONFIG_PATH"
export MANPATH="/opt/mono-2.10/share/man:$MANPATH"
export LD_LIBRARY_PATH="/opt/mono-2.10/lib:$LD_LIBRARY_PATH"
export MONO_THREADS_PER_CPU=75

5.- reboot your server

6.- install and launch the latest Aurora-Sim from https://github.com/aurora-Sim/Aurora-Sim

NB: if you wanna install mono 2.8, grab the install_mono2.8.sh instead of 2.10.sh

Have fun !