From: Daniel Bird dbird@sgul.ac.uk
Setting locking = No in the globals of smb.conf fixed it.
Keep in mind that: "Be careful about disabling locking either globally or in a specific service, as lack of locking may result in data corruption. You should never need to set this parameter."
Trying again since it didn't seem to make it last time:
Well, re-exporting NFS imports via Samba is not really a supported way to do things either, exactly due to the problems the OP is encountering. So, if you are going to live on the edge, you may have to get closer to it to get things to work.
This is usually an NFS issue, not a Samba one. Try setting "posix locking = no" in smb.conf.
Ian