There is an issue with upgrading to NAC 4.9 when on 4.8.2 that we discovered in our Test Lab environment. Our CAMs were successfully upgraded but our CAS had a fatal error, during the upgrade process, and made the CAS un-bootable. We had to rebuild the box back to 4.8.2. TAC has a bugID for the problem and it's currently in the "catastrophic" severity level. Hopefully they'll have a fix shortly.
-Chad-
