What is wrong with my break lights?

Yesterday a co-worker informed me that my break lights are both out. The little one on my windshield still works though as do the turn signals. I just replaced one of the break lights about 3 weeks ago so I'm not sure that the bulb would be the problem...but maybe? I need to get this fixed ASAP as my job involves a lot of running around in my car. I drive a '97 Ford Taurus LX. Could it be a fuse or something? Could both bulbs really burn out at the exact same time like that?