Unable to run .net app with Mono - mscorlib.dll not found (version mismatch?)

I have a simple .net command line tool written and compiled under Windows, using .net 3.5SP1. I would like to run it on Linux using Mono. I am using Ubuntu 12.04, and installed Mono Runtime using the Ubuntu software center. If I try to start my app in the terminal by doing: mono MyApp.exe I get the error: > The assembly mscorlib.dll was not found or could not be loaded. It should have been installed in the 'usr/lib/mono/2.0/mscorlib.dll'. If I navigate to that location, I see that it does not exist. However, there is `usr/lib/mono/4.0/mscorlib.dll` (and some more DLLs in the same folder). So seemingly there is a version mismatch. [in case it matters, `mono -V` shows `Mono JIT compiler version 2.10.8.1 (Debia 2.10.8.1-1ubuntu2)` ]