I've actually got both a general question, and a specific problem.
The general question is, when is it OK to use the same MFC object in two threads? The book I am reading (Kruglinsky) is somewhat vague and says that this can't ever be done safely, "except simple classes like CString". What constitutes a "simple class"? Also, if I ensure that an object is only accessed by one thread at a time (using critical sections, for instance), will it then be safe to use the same object in two threads?