vtkWin32OpenGLRenderWindow doesn't use multisampling when windows is created with a parent.
This issue was created automatically from an original Mantis Issue. Further discussion may take place here.
After investigation, it appears that the only problem is that when the WindowIdReferenceCount is higher than 0, vtkOpenGL class name is not defined, even though it is necessary later to enable the multisampling. Taking the vtkOpenGL outside the if statement corrects the bug. Patch is for current nightbuild, but could be very easily ported on any other version.