I've been searching all over the internet for a solution to this problem but so far have not found anything. I've come across several threads where people have an issue similar to mine, but nobody seems to be experiencing the same problem I'm having.
A few days ago my PS3 could not see my PC as a media center. This had worked fine once I figured out how to get Windows 7 to share media files as a media server. I didn't have time to look into it at the time, but today I started to investigate and found out that my computer is no longer part of the Homegroup we have set up here. One of my roommates is also running Windows 7, and before the problem started we could easily share files. The problem seems to be that I do not have a home network connection, yet I can still access the internet just fine.
When I go into the Network and Sharing Center I used to have the diagram showing My PC --- Home Network --- Internet, and had our Home Network homegroup in a section right below that. Now I just have a message saying "You are currently not connected to any networks", and below that I have options to set up a new connection or network, connect to a network, choose homegroup and sharing options, and troubleshoot problems.
"Connect to a network" (the obvious choice in this case) just pops up an error over my task bar saying "No connections are available". If I choose "Set up a new connection or network" it asks what kind of connection I want. When I choose "set up a new network" it scans for a network device and never finds anything. When I try to choose a homegroup it tells me that the computer belongs to a homegroup. It then tells me that the homegroup is not available because I'm not connected to the home network. I've checked the sharing options, and everything is "On" for both Home or Work as well as Public.
As for troubleshooting, I've tried just about everything I can think of. First I tried the built in troubleshooter for Windows 7. I tried troubleshooting incoming connections, network adapter, and homegroup. None of those come up with any solutions. I've tried disabling my network adapter, rebooting, and re-enabling. I've uninstalled and reinstalled my network adapter. My motherboard has 2 built-in gigabit NICs, one of which I keep disabled by habit because XP always tried to bridge them, and it annoyed me. I've tried switching between the two, and the problem exists regardless of which one I use.
Due to my network configuration each of the PCs on my network is manually assigned an IP address instead of using DHCP (we use some minor port forwarding on our router to run game servers). For the sake of testing I switched everything to automatic configuration, which resulted in the aforementioned active network diagram showing up, but the home network could not be recognized and I could not access the internet.
During my search for a resolution I came across a few posts talking about connection issues arising after the latest windows update. To test this I first tried to uninstall the last update I received, which was last week. I then did a system restore to a point last week before the problem started. Neither resolved the issue.
At this point I am out of ideas. If anyone has an idea for me to try I would appreciate it.
Edit: This is a wired connection BTW. Connected to a TrendNet Wireless N Gigabit router via CAT-6 cable. I've tested the cable on another device, and I DO have internet connectivity.