It's a test build because its source code has been updated after months of MAMEDev "brainstorming" (no offense, it was needed I think...) with official MAME code. So some of MAMEUIFX features have been updated to the new C++ MAME structure but even if they passed the compile process, they could not work as expected. That's all. Though I received until now only positive feedbacks so the next version will be released (hopefully) quite fast after the official 0.143u8 will be out. To know more about FX: http://mame32fx.altervista.org/features.htm The page has been updated to 0.143u7 but the download section and the news page are still on the old 0.141.