Headcase, what kind of ISP do you have? This often limits your capabilities w/ audio/video files. Your computer's memory could, as said previously, be affecting your experience, also.
As for JamPlay, I've just picked up the guitar again after a 35 yr layoff. I like the lessons (I'm taking them so I don't fall back into some bad habits I had when I played in my teens and 20's......guitar habits, not the other kind). They take you smoothly from one skill to the next, building on the previous lessons w/ good exercises to develop your skills.
Don't be afraid to click 'STOP' and practice the chord changes, pick patterns...whatever....before continuing. These lessons aren't timed and you can move at your own pace.