I'm trying to get my head around really basic animating. All goes ok until I try to replay/loop what I've created. I just get a grey screen with a few flickering areas.

What am I doing wrong???

Hard to say with the information you've given, but check your cameras. Your camera might be not be showing your figure, either because it's pointed the wrong way or it's blocked for some reason.

You might want to disable animation in the camera you're using (under Properties on the Parameters palette), at least for now. Then make sure your figure shows before you play your animation.

randym77's suggestion of disabling camera animation is a good idea, in case the problem is wild spline interpolation of camera movement.

If the camera isn't spinning wildy, un-tick this little skip frames pinball button; if you have a weak video card or are relying on an onboard video chip, your video chip/card may not be capable of replaying the preview in real time.

If it still sluggish in replaying the animation frames, try setting the display style to something simpler (which will display quicker), such as hidden line; that's the fourth "billiard ball" icon, or use Ctrl-4 from your keyboard.

Last resort is to simplify the tracking mode; the crudest mode will look like a man made of boxes, but if you need to see the motion in real time, it might be worthwhile. Look for these three icons beside the document window: