Had this same type of problem which i had attributed to updating the firmware on my router but after reading these posts i checked and did note a recent Windows update. Also, I am not a PC guru like a lot of the respondents on this forum. I just had a frustrating problem and wanted to share how I solved my particular problem (which was quite easy, 10 hours later, haha)
Did not read all the threads herein but i tried many solutions including the Bonjour, power cycle modem and routers, updating drivers, disabling, reinstalling, etc and none worked for me. Also tried system restore and that did not help either.
Here is a list of my PC sickness symptoms and see if they relate to yours:
1. Could not connect to internet via wireless connection.
2. Network was listed as "Unidentified Network".
3. Was unable to change the network type to private or home.
4. Could connect to internet via a port on the router (ethernet cable, obviously)
Solution to my problem (need to be connected to router via ethernet cable):
1. Open Networking and sharing center
2. Select Manage wireless networks
3. Under networks you can modify, "remove" all networks.
4. Open router administration via internet explorer
5. I have a linksys router and assume this will work on any type of router ... but as I mentioned, not a PC guru.
6. Restore router to factory defaults.
7. Click on wireless connection view in bottom right of tool bar and should see "linksys" or router name under wireless network connection.
8. Connect to wireless network. My router asked for a network security key which i had to get from within the router setup, but once i entered this key, i was connected.
8. Go to Network sharing center and should be able to see wireless network.
9. Should be able to unplug cable and still be connected to internet.
10. Go back to router setup to set up security
This may not be the exact situation you have, but after reading some of the suggested fixes to your issue, it appears there may be some commonality. After I spent all that time trying all the fixes everyone mentioned, I was relieved how easy my problem was to fix.
Good luck.