I think you are using AO on a light - ? - and this is related to the scene AO bias setting.

Open the Properties palette of the light with AO switched on, click into the Scene AO options, and reduce the bias value. Start with around 0.05 inches (you will need to convert that to whatever Display Units you are using, if you are not using inches) and take it as low as you can until you start to see black artifacts on the figure's skin, then increase it a bit to get rid of those artifacts.

That should hopefully sort this out for you.

(edit) hborre - yes RT is on, otherwise there would be no AO

"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)