Has anyone seen this? We had about 30 APs drop off the network after a controller upgrade and had to be manually assigned an address. We found that the APs are DHCP and have a reservation in the excluded range of the scope. In the new version of DHCP in Server 2008r2, even with a reservation in an excluded range, DHCP will not issue those addresses to clients. Deleting the reservation and letting the AP find a valid address in the range didn't work either.