Some more info on SAN / NAS / QlikView situations:
As Rob said, this problem has been around for quite some time (I first encountered it back on 10 SR1). As I understand it, Qlikview utilises a feature called partial file locking which only appears to be implemented on Microsoft Windows based shares (and is generally not implemented on unix based storage).
The issue manifested itself for us with the entire QVS hanging every couple of hours (10 SR1, SR3). As soon as we moved the mounted QVS folders off unix based NAS shares, the problem went away. Our temporary work around was to mount the Unix based network storage as a LUN in the server, and then expose that as a Windows based share in order to gain the partial file locking capability required by the QVS. In addition to the performance hit, the obvious downside of this is that we introduce a single point of failure (the windows server hosting the share), and that manual intervention is required for failover scenarios (as we need to remount the storage in another Windows based server if we lose the server hosting the share for some reason).