Disable Quick View/Quick Look for network volumes
Quick View in Mac OS X can cause a lot of trouble on network volumes. Users get ”access denied”, are unable to copy files and so on. Of course you can delete Quick View completely, but another way to do it is to deny access by path:
sudo nano /usr/share/sandbox/quicklook-satellite.sb
and add the following line at the end:
   (subpath ”/Volumes/the-name-of-your-network-volume”))
And there you go. No more pesky file locks, at least not caused by quicklook.