Car lunges forward while foot on brake

I actually saw the exact problem on your website "started lunging forward randomly". My new Subaru has done this about four to five times since I bought it in April. I will be at a stop light with my foot on the brake and suddenly the car lunges but does not move because my foot is on the brake. At first I thought I was imagining it but this Monday it happened and the force was great enough that I thought I had been hit from behind. It is very quick just as described on your website. It is at the dealer right now but they told me yesterday that they had never heard of this and sort of implied that possibly I was imagining this. I am afraid to drive the car. I am waiting to hear from them now. Any thoughts you may have for me would be greatly appreciated. Hopefully someone in the service shop will look this up on line like I did!