I've had the same issue but just using lion server.
The article mentioned above
Is of no help. Already using server 10.7.5 and the terminal command returns loaded. So the 2 suggestions are not applicable.
Does any one have any other ideas.
Had the same issue today randomly and found a thread stating that "Apple knew about this and was working on it". I solved it trying all of theses steps each on their own and it did not work BUT did work in this order for me.
-On the server shut down airport utility and server app if you have them open.
-Go to /Library/Server/ move Network folder to trash and empty
-Open the keychain and search for airport, erase all that come up
-Command line steps (so in Terminal)
sudo rm /var/db/.ServerSetupDone
sudo /usr/libexec/PlistBuddy -c "delete :managedIGD" /Library/Server/Network/Config/autoportmap.plist
sudo /usr/libexec/PlistBuddy -c "delete :lastIGD" /Library/Server/Network/Config/autoportmap.plist
(at this point it should say it can't find 'lastIGD")
-open airport utility and enter password for airport app leave open
-open server app, run through config then enter password for airport
This was basically all of the steps I found on various forums and seems to be either a keychain permissions issue or some funky server app issue.