Sound Issues – HMH Math on the Spot Review

After installing this application on my iPhone, I tried to view the "How to use HMH Math On the Spot" video, however, no sound could be heard when the video was played. My phone is running iOS v5.0.1. This appears to be a nice application, but without the ability to hear the instructor, value - worthless. Is there a known fix that I have not been able to figure out?
Review by nfarner on HMH Math on the Spot.