From the visual prefs guide (known bugs section) :
"Certain windows of some MUI programs (like IBrowse) appear empty if the top border's thickness is different than (titlebar height increment + 2).
This is really a nasty problem, I don't know if I will ever be able to find a solution.
For now, set the top border to a value == (titlebar height increment + 2).
Similarly, if (and only if) the screen's titlebar height increment is set to a different value than the window's titlebar height increment, you could experience "disappearing" titlebar gadgets in some MUI programs. "
Regards,
Lloyd