http://bugs.winehq.org/show_bug.cgi?id=15232
--- Comment #3 from Florian florianskarten@web.de 2008-09-11 02:49:07 --- I tested the application at http://bugs.winehq.org/attachment.cgi?id=5777 (again ?) at windows and the button gets overdrawn there too.
I uploaded source and binary of the version where the main window has the WS_CLIPCHILDREN style. In this new version the button is visible when the Application gets executed by windows, but not when the application gets executed by WINE.