After some more playing around I found a setting in the menu that lets you set how long the display will stay on after you change an input. It was set on a few secnds, switched it to on and all good.

This update was released back in May of 2008 I think but I didn't have the energy to pull out the 990 and do it. Now I was installing all new cables and an HDMI switcher so while I had it out, did the update. It's v3.24

Thanks.