husky07, My husband had the same problem (also applying to maryland) and email the public policy graduate school. He recevied a response today, saying that they resend the notifications to his recommenders and that the email might arrive at the spam inbox, so recommender should check if this is the case.
I am having the same problem, I submitted my application on dec 10 and my recommenders have not yet recevied an email. I sent an email to the graduate school but I haven't receive a reponse.