Reason?

[lordiron]

See Image. Awesome Program, best on the market, thanks. Why can't i use alt-print for image-capture?

[mouser]

You *can* use alt+prtscr to capture the current window.

That message is triggered when you try to capture the "Active" window using the System Tray Icon right-click menu; the reason you get that message is because when you click on the system tray menu, the active window loses focus, and so Screenshot Captor doesn't know what it was and so can't capture it.