Oddity when working with spheres

Noob here, been playing with Blender for about a week. While going through the build-a-virus-picture tutorial on this page – http://www.blender.org/education-help/tutorials/ – I found that when I tried to extrude the faces on my icosphere, some were extruding outwards from the center like I wanted, but others were sinking into the sphere. I deleted and started over several times before deciding I was making some user error and moved on to another tutorial. The next one was the explosion tutorial on the same page referenced above. This also involved creating an icosphere (well, a hemi-icosphere), but used it as the basis of a particle system. When I did that and animated it, I noticed that a large chunk of particles were moving inward towards the center of the icosphere when I was trying to get them all to move outwards from the center. So now that’s two completely different effects involving icospheres where I’m trying to get bits and pieces to all move out from the center, but some are moving in. I rendered an image of the first example as a reference. It’s available at http://twitpic.com/5cp72n . I think a fundamental setting is messed up somewhere. Anyone got a clue where I’m going wrong?

Recalculate the spheres face normals. In edit mode select all the faces and press Ctrl+N (or the button in the toolshelf)

You are extremely awesome. That did it! Thank you!