This may turn out to be a real silly thing, but i'd just like to know because at the moment i cant get a custom light to work, and anything else i work within the game turns off, and i dont want to save it incase it causes an issue.

Thankyou.

The same thing happens to me, and it is quite annoying. I don't think it effects anything in-game though. If you move one of the objects in the render window after that happens, it will update showing the light, but just on that object.

There is a problem with the geck...you need to use the F5 key and re-render the window. It's a pain, but no other fix has been found yet.

This just adds to the list of things they (Presumably Obsidian) screwed up with the geck, *Sigh*