Running .NET 4 application with Mono

I suspect the exception is because the method System.Windows.Forms.Application.SetCompatibleTextRenderingDefault hasn't been implemented. Have you ran the tool through the Mono Migration Analyzer (MoMA), should help in knowing whether your application is compatible with mono. From that point you can possibly workaround the problem, maybe even incorporating the missing method in your code.

Sounds like you're experiencing this bug:

My Doc's Got No Nodes: .net 4 Client Profile on Mono 2.8

That is assuming you installed > Mono 2.8 (which was the first release to support .NET 4.0). If not, you should install a more recent Mono package.

The other thing to keep in mind is that Mono doesn't support the entirety of WinForms. Unless you developed your application with Mono in mind, there's a good chance you'll find that something you used isn't supported.