Yesterday my application worked fine. Today, when I try to start it (from the Visual Studio) with the F5 key, the icon appears in the taskbar (Windows 7) but nothing on the screen. Clicking on this icon does nothing. Right-clicking gives only the option to close the window or pin it to the taskbar. If I change mode from "Debug" to "Release" then all is well and I get my initial opening screen. I changed nothing between yesterday and today, so what is going on here?