A network always has a SSID, but may simply not be actively advertising it. Disabling broadcast SSID isn't the same as disabling the SSID. When you disable the broadcast, the SSID isn't included in the information that an outsider would see displayed.
When the SSID is not broadcast, the agent you are using would not be able to pick up the SSID. So, you need to know the SSID which is being set on the access point. Manually giving the SSID to the agent is the easiest way of using the network.
From Force Vista To Connect To Wireless Network When SSID Is Not Broadcasting:
There is actually an easy fix to force
Vista to connect to Wireless Network
that is not broadcasting its SSID.
Just open up the Network and Sharing
Center by clicking on Start, type the
word network in the Start Menu search
box and click on Network and Sharing
Center link in the search results. Or
go to Start \ Control Panel \ Network
and Internet \ Network and Sharing
In the left navigation pane, click on
Manage wireless networks.
Then right click on your wireless
network connection and select
Click on the check box next to "Connect even if the network is not broadcasting" and click OK to save the
change (no reboot is necessary).
Now when you need to connect to
wireless network, when SSID is not
broadcasting, Vista will make the
connection all the time.
Also, as far a security goes, there is
no real advantage to hiding the SSID
since many programs can see your
wireless device when it is not