typo on the official degree from University of Denver

I started taking classes for my Masters in September 2005. I finished my thesis the end of May 2011. I officially graduated in August 2011. I received my degree from the University of Denver in October 2011 and it said I graduated in June 2007. Buzz kill!!! I had to call them and tell them about the error; to which they told me to send back both the unofficial transcript and the degree certificate so they could replace them both. They could not explain the error. Ridiculous. I have the corrected degree now; thus it is offical- I have completed Graduate School. YES!