Hi justmyheart1989 and welcome to the Q&A Board!
The S2 is an advanced digital camera and, like other advanced cameras, it can take some time getting used to. You're willingness to learn will pay off, believe me.
If you're manually setting the shutter speed, you may have set it too high so not enough light gets through the camera lens. We have some useful information explaining the differences between aperture, shutter speed and how they relate to one another:
Aperture:http://www.digicamhelp.com/advanced-digital-camera-settings/aperture.htmShutter speed:http://www.digicamhelp.com/advanced-digital-camera-settings/shutter-speed.htmAction shots are best when they are taken in good light, the brighter the better. This section on taking action photos should be useful too:
http://www.digicamhelp.com/how-to-photograph-sports-events/After you take a look, please feel free to come back and ask further questions.
btw, if you haven't done so already, you may find my
S2 BLOG helpful. It contains lots of suggestions for getting the most out of the camera:
http://www.digicamhelp.com/canon-s2-blog/index.htm