Lost network connection shows "Unidentified Network"
No network connection because of multiple networks.

Note: We had this problem on four of our computers using both Vista and Windows 7. This started soon after a Windows update however we can't be sure when or why this occurs.

After startup, the network connection to my local network sometimes fails (yellow triangle with exclamation mark over the tray icon). A "Unidentified Network" is added and you have no network connection.
The only thing that fixes it is to go into my network connections window and disable the network adapter then re-enable it (then it connects to the internet fine). But usually only until the next startup.

After much searching and testing we found a fix.
It is actually the Bonjour DNS Responder Service causing the "Unidentified Network."
The Unidentified Network disappeared after stopping this service. It seems like it it conflicts with a newer Windows update since it happened on four of our computers running Vista and Windows 7 soon after doing a Windows update. If anyone know more about this problem please let us know. Win7tips@gmail.com

Fix:
After disabling the Bonjour DNS Responder service, the problem has gone away! I can now reboot and my network adapter comes up without me needing to disable and re-enable it.

You can't see any name such as "Bonjour DNS Responder service" in the services list. You must look for "Id_String2.6844F930_1628_4223_B5CC_5BB94B87 9762"

Steps to take
Start > Run
type: services.msc
Look for: Id_String2.6844F930_1628_4223_B5CC_5BB94B87 9762 in the list
Right Click
Select Properties
From the startup type drop down select Disabled
Click STOP
Click Apply

More about "Bonjour DNS Responder Service" is here:
http://www.raymond.cc/blog/archives/2008/02/10/how-to-uninstall-or-remove-bonjour-mdnsresponderexe/