Are you using AO? Are yourendering with raytracing or the P4 rendering engine? What figure is it? We need a little more information before we can help you.

Assuming you're using raytracing:

If you're using AO, there is a problem with self-shadowing polygons that can be corrected by increasing the bias on your AO light. If it's a backfacing polygon problem, checking "Remove Backfacing Polygons" in Render Settings should make it go away.

Otherwise, tell us a bit more about the problem.

It's all fun and games...
Until the flying monkeys attack!!!