My photos are not sharp enough

Using my D5100 and the 55-200 vr I tried to take some shots of my daughter on a horse. It was  about 4:00 pm with enough light but with some glare.

Well I had to use the maximum zoom of 200 to reach the far away action and I believe that there is a rule that says since I am using 200 mm so I'd better use a shutter of 1/200 or more. So I used 1/250 to 1/650 and thought that with the vr I will be well covered ....Problem is all my shots were soft and with motion blur (I think) ..Is a horse just walking steadily,too fast for 1/250 ?? Am I that unsteady at 200 mm ? or is the glare too much or the lens soft at its maximum zoom ? ..Sorry too many questions but I am still learning

Here are some examples

Nagy
Feel free to critique, pp my pics, post ideas,..etc.
http://img.photobucket.com/albums/v606/elraheb/Lovey_logo.jpg