BizTalk RPC error

Came across this really annoying RPC error at a client site.  One of their systems is still running BizTalk 2004 (this problem is probably still the same in BizTalk 2006). Basically they have 4 servers in the BizTalk group:

• 2 of them doubles as application servers and are on NLB.
• 1 is a fileserver which doubles as the SSO Master Secret Server.
• Last one is just a BizTalk server.

They wanted to replace one of the application servers, thus built a new server to join the BizTalk group and NLB. It all seemed to work fine except that we can’t administer BizTalk from the new server after we joined it to the NLB.  Opening BizTalk Server Administration doesn’t show all the receive and send ports. Running BizTalk Explorer at least gave error messages, though they didn’t make much sense:

“Could not retrieve transport type data for Primary Transport of Send Port ‘XXX Port’ from config store. Both SSO Servers (Primary=’SERVER1′ and Backup=’SERVER2′) failed. Backup server failure: The RPC server is unavailable.”

SERVER1 and SERVER2 are the two BizTalk servers on NLB. Neither of the two servers is the Master Secret Server, so why is it trying to connect to it? The reason it cannot communicate with the two servers on the same NLB cluster is because the NLB has been configured to use Unicast. Anyway, it shouldn’t need to communicate with either of those two servers, it just needs to communicate with the Master Secret Server.

The question is: where/what sets the SSO Primary and SSO Backup server values. Searching the BizTalk tables, I found that the SSO Primary server is set in the table adm_Group, under the column SSOServerName of the BizTalkMgmtDb database. Changing this value to the server name of the SSO Master Secret Server resolved the issue. Not sure where the SSO Backup server value is set though, not that it matters here.