Lately I've been using NFS to connect to a share on my Fedora virtual machine due to "shared folder" and Samba limitations. However, my virtual machine is not always available. Windows being Windows, if you follow the recommended procedures for mounting your NFS share (assuming Client for NFS is enabled [to begin with -- grief -- only on Windows 7 Ultimate or Enterprise]; it's installed but disabled by default -- more grief), Windows Explorer will become unresponsive. Also, rebooting will not fix the problem as Explorer will make it a permanent drive mapping. For the grand finale of grief, you'll need to modify the registry to fix access permissions from the Windows client.

All of the recommendations I found said to use the mount/umount command-line programs, installed with Client for NFS, for managing drive mappings. As I discovered, this was the source of Explorer's hanging. The solution is instead to perform the following when connecting:

net use <drive_letter>: <address_of_machine_with_share>:/<location>/<of>/<share> /persistent:no

and for disconnecting:

net use <drive_letter>: /delete

Thank goodness for that Windows for Workgroup certification, otherwise I wouldn't have made the connection and tried "net use"! Hope this saves someone else from similar hours of grief!