"Add server" should not work when server you're adding is already part of a cluster.

Created an attachment (id=313)
log from sever D (centos 5.2 64 bit)

Install ns_server 1.6.0beta1rc4 on 3 rhel 5.4 boxes [two 32bit (A, B), one 64bit (C) and the same date on 3 boxes]
http://screencast.com/t/MjAwMGYz
Install ns_server 1.6.0beta1rc4 on one centOS 5.2 64bit (call D) (different date with other three boxes)
On centOS box, click on "Add Server" button and add A (10.1.3.80) to D.
On centOS web console, I see 2 servers
http://screencast.com/t/NTc0YjYxNz
Two servers (10.1.3.107 and 10.1.3.112) are gone even reload the page. No pending Rebalance
All A, B, C and D web console, I only see A and D servers on server page.
http://screencast.com/t/YWE0MGZh
http://screencast.com/t/ZjM4NmZjNT
On the web console 10.1.3.80, it also shows 2 servers
http://screencast.com/t/NGY3N2Zm
On rhel 64 (10.1.3.112) is the same with only 2 servers
http://screencast.com/t/Njk2MjA1Yzk