Have you considered a vision test from a Vision Therapy doctor? My 8 yr old had some problems with writing, staying on the lines, not seeing all of the numbers in a math problem, etc, and she was diagnosed with Strabismus (very slight) and a convergance problem. She's getting eye therapy and has improved quite a bit. Just a thought that it might be eyes and not motor skills or brain-related.
http://www.covd.org/?page=Symptoms