Mine went strange last night. Turned it on, all that was there was a bright green screen. That went, to be replaced with a green (as you say) jigsaw effect. The box was totally unresponsive with the remote, so I turned off for about a minute, removed the viewing card, replace card, turned back on, and all has been well since.
The trick with turning it off for 60 secs, always seems to work. (They explained to me years ago, sometimes the box needs to reboot).