When using this function MB_DEFBUTTON2 is ignored. First button is always default.
What is your exact setup? Do you use custom buttons?
AdvMessageBox(0, L"Question", L"Title", MB_YESNO|MB_ICONEXCLAMATION|MB_DEFBUTTON2);
Button "Yes" is the default instead of "No".
We traced & solved this issue. The next update will address this.