When I was younger, I had a nightmare that I was having a nightmare and when i woke up i tried to get to my moms room at the other end of the house and i was being chased by zombies and they were popping out of each room... and when I finally got to her room and I opened the door she was also a zombie...
i woke up at that point and then had to make the same trip to get to her room... yea that was a ton of fun...

The meaning of the key symbol in your dream (zombies) should help you better understand why you had the dream. Here's a link to its definition on this website: dreamdoctor.com/component/dreams/?contro...task=details&id=2062

Hope that helps!