Sometime in the last three weeks, Vista's networking awareness broke. It was previously working since September, 2008 when I got the computer. Note that I said "networking awareness" and not "networking". I have no trouble connecting to wireless or wired networks, or PPTP or IPsec VPNs. I also have no trouble accessing shares on networks I am connected to, or printing to network or shared printers. I have no trouble connecting to the Internet or to servers via Remote Desktop.
The network status icon next to the speaker icon used to show a globe superimposed over the two computers when I successfully connected to a network, acquired an IP address, and the computer verified I had connectivity outside the gateway. If I got an IP address but didn't have Internet connectivity, it would show a yellow warning triangle over the comptuers. If there was no connection, it would display a red X.
Now, no matter what the status is, I have a red X. I'm currently connected to my home wireless network and clearly have Internet access, yet it is showing the red X. If I look in the Network and Sharing Center, it shows my computer and a globe representing the Internet, but it has a red X in the middle and the globe is grayed out. It also says "Not connected".
If I look at the Network applet, it tells a similar story. It says: "This computer is not connected to a network." If I go to the Connect to a network tool, it shows me as "Connected with limited access" on my wireless connection. This status would previously display the yellow warning triangle over the network status symbol.
This problem occurs 100% of the time in any network. At home wired or wireless, at the office wired or wireless, at customer sites wired or wireless, at a hotel I was at recently..
Here is some information about my PC:
Dell Latitude D531 laptop (all drivers fully up-to-date)
Windows Vista Enterprise SP2
Active Directory domain member
I have Vista SP2 installed, but my problem predates the installation of SP2. I installed SP2 hoping to resolve the issue. The problem seemed to just show up one day. I don't recall making any configuration changes or installing anything around the time I noticed the issue.
I also mentioned that this is a member of a domain. Group policy does not seem to be the issue because I work for a small office that is 80% Vista and no one else has this issue.