Problem solved, just need to right click the program on the taskbar and maximize the window, simply left click won't work!
I've been using qucs for quite a while under Vista and nothing has ever been wrong. However yesterday after I updated iTune to the newest version, qucs won't show up any more. And yet ou can still see the problem lie on the taskbar. I uninstalled it and reinstalled 0.0.15, 0.0.14, 0.0.12, but the problem remains. It'll be so nice if you can help me with it.
One way leads to another