SSO J2EE client change - dispatcher running, no server connected!

I need to set up SSO between the portal (SP9) and R/3 to enable users via our bespoke java application to send RFCs. help.sap.com recommended changing the J2EE client on the WAS so tickets issued by the portal would be unique (rather than using the default client 000). I made the change in cluster-data > server > services > com.sap.security.core.ume.service > login.ticket_client via the config tool and stopped and restarted the instance.

The MMC shows the system has started but I'm unable to connect to the portal - Dispatcher running, but no server connected! I restarted the J2EE engine via the WAS (we have WAS 6.4 ABAP + Java), no improvement.

I'm unable to connect to visual administrator. Connection via the dispatcher generates error - connection lost. Connection via the message server generates error - unable to look up connection parameters.

In changed the client value back to the default and restarted but still have the same problems.

1) How do I re establish the connection parameters without re installing the portal?

2) How do I avoid this problem? Should I just use the default client 000 and hope problems do not occur later when tickets are issued?

Thanks