"Attempted to read or write protected memory" error when passing a native object from C++/CLI wrapper dll

I have a big C++ project with an interface. I built a C++/CLI wrapper dll in order to communicate with the project.

It is built of managed classes, each holding a reference to a native object and functions wrappers. The project has a factory method creating an object and returning it as an abstract class, the main object inherits (lets call it IObject).

When calling the factory function "createObject" in C++ everything works well. Also in C++/CLI the object is returned and work properly. But in C#, after both of the DLLs are present and the managed one is referenced by the program, when I get to the managed DLL's "createObject" function the program crashes at runtime, saying:

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An unhandled exception of type 'System.AccessViolationException' occurred in wrapper.dll

Additional information: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

It doesn't seem like a marshaling issue, since it should only return a pointer to a native object.

I tried creating factory functions returning some structs and strings, and everything worked well.

I thought it might happen because the abstract class object (IObject) returned by the factory function is smaller than the object itself (Object - which inherits from it), so the object contains more data than the size of IObject should. But this is how factory patterns work! I see no other way.

Thanks in advance.

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My guess is that you have a bad pointer in your C++ code somewhere. When calling in C++, it doesn't care, but when calling in C#, it protects the memory more.

Just a guess, but hopefully it's pointing in the right direction.