Try this...
Check to see if you have this little devil in your services list:
"##Id_String2.6844F930_1628_4223_B5CC_5BB94B87 9762 ##"
If you do, stop it and disable it. It is actually the
Bonjour DNS Responder Service, and I believe it is the cause of the
"Unidentified Network."
The Unidentified Network disappeared after stopping this service and a quick disable/enable of the NIC, restoring Internet access.
I Actually just rebooted, edited this post, and then re-enabled the offensive service to see what would happen...Immediately after enabling the NIC and this bastard service, the "Unidentified Network" returned...stopped it, disabled it, disable/enable NIC...Internet back up and running and no "Unidentified Network." (woot - woot!)
Hope that helps! I haven't had issues since...
FYI - I experienced this in both build 7100 and 7127...I am running 7127 now x64 - and discovered this fix just last night...so far so good just rebooted and then edited this post...I believe this fix will solve 7100 build issues too; however... I have not tested 7100 again yet.
...I also re-enabled Win 7's Discovery Mapping services, but always leave IPv6 disabled just because I am not using it.
...another two reboots, and a hard disk addition, and no problems with the Internet! - If you tried another fix such as changing the address of your network adapter, under "Advanced" - this is not necessary...I set mine back to "Not Configured." Everything is working fine as long as the Bonjour service is not running...
My system:
ASUS P5E
Quad Core Q6600
4GB Corsair Dominator DDR2
NIC: Marvell Yukon 8E8056; driver v10.69.2.3 (4/21/2009)
***fyi - i did update the default Windows driver with this, Vista x64 driver
For the record, there is some blame pointing towards the following software, of which I do have installed and running properly:
Office 2007 SP2
Adobe CS3 (updated current)