Looks like we need to change our dates guys! 
Did some Googling and 1st-3rd June is Rock am Ring - think Glastonbury for rockers, but bigger. The whole area gets wrapped up in the event and they use the old Nordschleife and surrounding areas for camping, hence no dates at all for circuit driving.
http://www.rock-am-ring.com/
http://en.wikipedia.org/wiki/Rock_am...d_Rock_im_Park