Changed host IP address - Navishphere reports Unmanaged

I've been banging my head on this for a while, I'm sure it's not uncommon.

Configuration:
(1) EMC CX-300
(2) Brocade Fibre Switches
(3) Dell Servers (S1, S2, S3)
w/ Brocade Fibre HBA
w/ Dual NIC 'bonded' to single address
w/ SLES 10 SP2

Old IP addressing (name and address simplified for discussion)
S1 - Address 1
S2 - Address 3
S3 - Address 5

New IP addressing
S1 - Address 1
S2 - Address 2
S3 - Address 3

As you can see S3 now has the address S2 used to have. In Navishpere S3 has a "U" icon and now reports as 'Un-managed', this is seen in Right-Click Host > Properties > Agent Tab > "S3 is not a Managed Host, unable to retrieve Remote Agent Configuration". However it shows connectivity, and all hosts can see the LUNS.

I have tried adding system@SPA_IP system@SPB_IP to agent.config but it makes no difference and then makes this host 'non-standard'. I have tried uninstalling and re-installing the agentcli (6.26.9.0.51-1) as well as stopping and starting the naviagent - and of course rebooting in between. Firewall is off.

After the above if I use Tools > Connect host and enter the IP of S3, it reports:
Errors encountered while retrieving information for this host. Please check the host ip address. Either this host is not managed or is not connected to a CLARiiON storage system. However if I then go to a Storage Group and choose "Connect Host" it sees S3 and lets me add it to the storage group, but it reports the OS as "Unknown"

S1 and S2 look normal and do not have any problems. None of the servers have DNS entries at this time but hosts can ping SPA/SPB by address. Can't see any other problems with the setup or connectivity but maybe I've missed something (I'm certainly no SAN pro).

Any help or suggestions would be appreciated,
Thanks -Bruce