[ubuntu-us-ut] stopping network manager

[jtaber]

How can you turn off network manager?  ie you're at a cafe - you connect
to the wireless, get some email, now you want off the wireless system to
work on some confidential stuff.  Just right-clicking on icon to turn
off wireless doesn't seem to break the connection (or it restarts
itself).  Is there a command line like /etc/network-manager off  or some
such