rndc connection failing after upgrade

[David W. Brown]

Hello BIND and rndc gurus, I upgraded to 9.2.3. the named daemon is running and answering queries but the rndc utility returns the following error condtion:

rndc: connection to remote host closed
This may indicate that the remote server is using an older version of 
the command protocol, this host is not authorized to connect,
or the key is invalid.

The key seems to be valid. I ran rndc-confgen -a which outputs a rndc.key file. The rndc.key file is included in the named.conf. Any suggestions? Please advise, David.

OS: rh7.2
BIND: 9.2.3