OES2 SP1, 2-node cluster

I had a server unmount an NSS volume with the message below in the logs.
Any ideas what could have caused this?

SAN_SERVER is the cluster pool.
USERAREA is an NSS volume in the pool.

Code:
May 21 10:21:21 vishnu ncs-resourced: resourceMonitor: SAN_SERVER.monitor failed 256
May 21 10:21:21 vishnu ncs-resourced: resourceMonitor: SAN_SERVER 1 failures in last 600 seconds
May 21 10:21:25 vishnu adminus daemon: umounting volume USERAREA    lazy=1
May 21 10:21:25 vishnu adminus daemon: Failed to delete the directory /media/nss/USERAREA.  Error=39(Directory not empty)
May 21 10:21:25 vishnu adminus daemon: Entries for Volume USERAREA from pool SAN are not removed during pool deactivation
May 21 10:21:25 vishnu kernel: Waiting for 2 Inuse beasts to unlink
... repeated multiple times
May 21 10:21:36 vishnu kernel: fastReadCache - Buffer's should always have an inode
May 21 10:21:36 vishnu kernel: isCached - Buffer's should always have an inode
May 21 10:21:36 vishnu kernel: isCached - Buffer's should always have an inode
... repeated multiple times