Screen Capture Disabled

[anecdote1]

Hi there,

Out of the blue 'shift+Command+3', and 'shift+command+4' are not working. I can hear the camera clicking sound and a .png is saved on the desktop but it is always a stripy image. See example.

I'd be very grateful for any help

Thanks

 

[Corrosive vinyl]

have you changed anything recently? downloaded anything?