Photoshop :: Erase Writes And Write Does Nothing?

I have Windows 7 and Photoshop CS6 that I bought today.  I was playing around with new brushes I downloaded today and all of a sudden they stopped working.  They wouldn't write and then I got this idea that maybe they were erasers and not writables.

Well they did not erase, they wrote and not in my primary color.  Then when I went to show my husband...all of a sudden they worked correctly.  Then I went on my merry way playing with my new brushes and they broke again.  I am going to try to include pics here but I am not real good at HTML.  It just seems easier to show you what is on my screen than to describe it.

So, the first picture is when I used my brush as a Brush Tool as you can see.  I had to zoom in so you can see how many pixels it actually wrote.  As you can see the brush is much larger.  This is the second time it did this.  The first time it wrote many more pixels, actually looked kinda cool with this faded ink kind of look to it.

The second is what happened when I tried to erase my coloring.  As you can see, it choose the secondary color.  I am not at all sure why it would choose that color of all colors.  Like I said, I know nothing about computers and I am learning Photoshop.