NFS: Network disconnect causes Gnome Nautilus to hang / Jumping progress bars
Solution 1:
I also have the first problem reported, but no answer for it. The copy also tends to lock up other parts of the system (perhaps due to Nautilus' ubiquity as a GNOME service) while the copy goes on.
On the second point, I found this SO question very useful: https://stackoverflow.com/q/40317/91808. In particular the umount -f /mnt/nfs
suggestion worked for me when nothing else did, saving me from an irritating reboot.