I actually write in .NET a lot for my paying job (it pays the bills), but I've never attempted to develop .NET on Linux and wouldn't really know how to compile it let alone debug it... that's why I didn't respond...
I assume you're using Novell's implementation of .NET to compile (I can't for the life of me remember the name of project), is that correct?
System.Windows.Forms is a pretty basic forms class used only for basic GUI. Most, if not all, .NET projects reference more than that. Your actually problem can also depend on the version of .NET it was supposed to be compiled against as well...
I have come across many differnt bugs in Microsoft's implementation of .NET that I had to workaround by directly implementing the Windows API... you may want to check that the project doesn't attempt to do that (you wouldn't receive compile errors if the it only implements the Windows API based on the OS it's being compiled against using the interpreter)... but again I'm talking Windows and I'm not sure what impact that would have when trying to compile on Linux...