You saw this, right? http://support.apple.com/kb/TS2923
Are you still using one system as client and MDC? If you now have multiple Xsan systems, does the error affect all systems or just one/some?
Did the IP address of your system change? Make sure that the IP address of the MDC(s) in /Library/Preferences/Xsan/fsnameservers matches the current IP address of the MDCs. If it doesn't, fsmpm will bail out when it can't talk to an fsnameserver.
If fsmpm isn't actually running (check the process list to be sure), check the nssdbg.out log to see what's happening when fsmpm tries to start. /Library/Logs/Xsan/debug/nssdbg.out
Make sure you're not trying to do anything crazy like using WiFi for your metadata network.