On an MDC, what does /Library/Filesystems/Xsan/bin/cvversions show? What about the contents of /System/Library/CoreServices/XsanVersion.plist?
Maybe there's some bad info in a cache somewhere. Close the window in Xsan Admin and click disconnect. Then go to File -> New -> Connect to existing SAN, and reconnect to an MDC. If that doesn't help, try trashing /var/servermgrd/servermgr_xsan.lock then restarting servermgrd (or reboot) and then reconnect again in Xsan Admin.