Hey!
Don't panic! Don't beat yourself (or other people) up for this mix-up. Bureaucracy will always be evil; particularly in medicine they want to find more excuses to weed people out. As Bill Gates said, "Life is unfair. Get used to it."
On a more positive note, I guess what I have to say has largely been said by persons above. Just sit it this year. One of my mates is actually resitting the umat in 2007 - doing Advanced Science for now and going to try transferring.
And Graduate Medicine is definitely a great option. I believe everything happens for a reason - perhaps you are meant to do graduate med because something amazingly special awaits you at that particular university. Okay so I'm being romantic and idealistic, but don't we have the right to dream?
Anyways, good luck on your medical journey