If your password is not there then you could be on someone elses network , when you set up your network with a modem and router then the router automaticly registers the password on your computer. If it's not there then take an ethernet cable and plug into the router and you should then be able to get your password just use your user name and password and go into the router and the network password is in the router.
Are you on a domain, connected to multiple resources? One of your connections may have dropped (e.g. to an Exchange server, if present). Did you change your domain password recently? For either of these issues, a logoff / logon may take care of the problem, or provide further information, such as an error that your account is locked (call your Help Desk).