pcarthy, did you get this worked out? This is one of the most common mistakes for beginners to make and soooo confusing at the time. I made this mistake too when I was starting out and it was very frustrating because I KNEW that I was doing a knit and a purl stitch perfectly, but something was way wrong. LOL
The video should have you straightened out. Just remember to always have the yarn in back when you knit and in front when you purl, and to move it from the two positions between the needle tips.
Don't give up. You'll have your head start when you begin your classes.