[vtkusers] linking problem with inheritance [urgent]

[imho]

Hi,
I try to make a custom interactor, so

class vtkInteractorStyleCustom : public vtkInteractorStyle
{
...
}

but I have a linking problem :/
vtkInteractorStyleCustom.obj : error LNK2001: unresolved external symbol 
"public: virtual char const * __thiscall 
vtkInteractorStyle::GetClassNameW(void)" 
(?GetClassNameW at vtkInteractorStyle@@UAEPBDXZ)

What do I have to do?
Thanks