int main()
{
   MTestClass m;
   m.MTest();
}

Fixing your code so that it doesn't use __gc, has no errors and has a
main method caused a clean compile when /clr is used, and a warning
when not used. I don't know why /clr is affecting this.

Tom

I've done some tinkering, and this is the minimal program I can write that
exhibits the behaviour:
----
class X
{
public:
   ~X() { }
};

class Y
{
public:
   int test()
   {
       X x;
   }
};

int main()
{
   Y y;
   y.test();
   return 0;
}
----

This code correctly causes the error message without /clr, but incorrectly
compiles with /clr.

The conditions for the bug occurring apparently is the presence of local
variable of a class type with a explicitly defined destructor. Remove the
destructor from X and the error is correctly generated. Remove the
definition of X x from Y::test and the error is correctly generated. Leave
both in and the error is not generated. Again, this only applies when
compiling with /clr.