Multiple Inheritance Problem

[_uj]

I believe that is still undefined behaviour (99.9998%), but much more likely to "randomly" work on 32 Bit Intel boxes at least...

You mean assigning a pointer to DWORD (an integer type) is undefined? That's true but if DWORD is replaced by void* it's correct C++ and should be portable.

Still the problem the OP reports persists also with void*. It has to be fixed the way I suggested, by restoring the typeless pointer to its actual type before upcasting.

So it's okay to make a pointer typeless by casting it to void*, but be sure to cast it back to its proper type before doing something with it. If not you get undefined behaviour

This is discussed in 5.6 Pointer to Void in Stroustrups C++ book.