Problem with compiling [Target framework]

Anytime anyone in my team opens Monodevelop for first time, or creates a new script, we have to manually change the target framework 3 times, for some reason. We compile, and it gives us the following error.

We change the target framework from "Mono .Net 3.5" to "Mono .Net 4.0" and recompile.

and after recompiling, it gives us the same error again, in a different script.

We go to general, and the option is again in 3.5. We repeat this process 3 times, and then it gives us no error.

We have to repeat this process everytime we create a new script.

Does anyone know how to fix this? I would love you forever. :)