Thanks, luv! :O)

That's probably it. Very strange that it should suddenly appear in the middle of several test renders.

Lights and render settings? Well, nothing special. I'll just reload the test scene and take a screenshot or two. Back in a few...

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)