Monnat is correct. I believe that what you are having is a simple problem, but a common one. During the upgrade, you likely went from a ZD firmware of 9.x to a SmartZone firmware of 3.x. When your AP rebooted, it likely lost the configuration of your controller. Your DHCP server is likely set with subcode 3 which allows the AP to obtain DHCP Option 43 and join the controller. You can do two things here. In your DHCP server, change your subcode option from 03 to 06 and reboot the AP so that it get the updated dhcp lease, this time pointing him to the vSZ.
Option two is for you to ssh to the AP and issue the aforementioned command: set scg ip x.x.x.x where x is replace with the IP of your vSZ.
That should fix your problem. Let us know if this gets your APs online..