[cisco-voip] 7936 conf phones

[Bellerose, Robert]

Question
I have a site with CME-CUE v2.3, 4 conf phones that have been
recommended by Cisco to swap out due to on hook off hook problems. I was
able to swap out the first conf phone 7936 by doing the following.

ephone  6
no mac-address 0004.f2e0.fbf0 (old mac)

ephone  6
 mac-address 0004.F2E0.5cb8 (new mac from replacement)
 ephone-template 1
 paging-dn 104
 type 7936
 button  1:6

I was able to have an end user set up the conference phone and he tested
and everything was working fine.
Now when I go to replace the other three sets the old mac address for
each of those phones that I have removed using the below command does
not seem to work.
ephone x
no mac-address 0004.f2e0.xxxx

When have the end user put conf phone on the port I try to program the
replacement conf phone the following is displayed. I had him put it on
an entirely new port on the same subnet too.
RTR(config)#ephone  6
RTR(config-ephone)#no mac-address 0004.f2e0.fbf0
RTR(config-ephone)#
RTR(config-ephone)#ephone  6
RTR(config-ephone)# mac-address 0004.F2E0.5cb8
ephone slot is already registered with 0004.f2e0.fbf0.
Cannot change MAC address.

Is there a cache that needs to be cleared? 
Thanks for any help.

Rob