“Network cable is unplugged” but its really not..

I have a desktop computer that is running on Windows Xp, up until this morning, everything was fine, I could connect to the internet with no problem.

I turned on my computer, and it is telling me that the network cable is unplugged, as well as my network is not showing when i go to “my network connections”

But yet…..

I AM connected to my router, and there is no problem with the cord (I tried it on different computers as well as my Xbox 360 on the same port….so I know its not the router)….when I go into device manager, everything seems to be working correctly, and my network adapter and ethernet card both are marked as working properly.

Any ideas how I can fix this issue ?