You're shooting the equivalent of a 400mm lens handheld on moving subjects. I'd say that chances are about 95% that your focus problem is actually blur -- *nobody* can handhold a 400mm with a high rate of success. Just the the fact that you have to press the release will jerk the photo around. *Any* vibration will blur it. Put it on a study tripod on a windless day and fire it with the timer, and I bet your focus problems will largely disappear.
Blur isn't the problem at all - I have hundreds of photos like these from Bolsa Chica (taken with the PanaFZ-50), and I'm accumulating quite a few from Ohio with the Pana G1. The FZ-50 is clearly inferior, with IS and a 420 mm equiv. lens, yet the focus success rate was about the same as the G1. In fact, with the G1 set to the default of not allowing the shutter to trip when the camera thinks focus can't be achieved, I was constantly pushing the shutter release and the camera wouldn't take the picture, so I turned that "feature" off.
After tens of thousands of photos with the Nikon 8800, Pana FZ-50, and now the G1, I have a really accurate idea of what the problem is, and the problem is that the G1 with the 45-200 just isn't much better (if any) than the 3 year old FZ-50.
And the point for prospective Olympus users is - use a short lens, or wait for good light.