Had similar problems photographing indoor tennis. I got a few tips that really helped me. The first is that you need to have a faster shutter in order to capture the action without blur, so I used 1/200 shutter speed (might even go a little more next time as the rackets were blurred with faster swings). I used an f-stop of 5, and cranked my ISO up to 2000 (to allow more light into the picture). I'm also using a Nikon D5000 with a kit lens (18-55 VR). I'm under flourescent (sp) lighting. No flash! All in Manual Mode. I'm not sure this will help, but it sure helped me. I was always afraid of ISO until I began learning about it.
If anyone has better advice, please chime in as I'm a relative newb.