I had some irritating problems, and used a few things on this post to try to correct my problem.
My problem was:
I was using wireless networking with netgear wg111T adapter.
My net notification icon was a square thing with a red X through it.
My network connection was working ok, though taking a while to recognise my network
from startup or wake up.
I opened network and sharing centre and clicked change adapter settings.
I noticed that my local area network (wired) adapter was not in the list of adapters.
The only one that was listed was my wireless network connection.
I went to device manager, found my local area network adapter, and disabled it, then re-enabled it. It still did not show up. I uninsatalled it, then re-installed it. Now it shows up in my "change adapter settings" area of network and sharing centre.
Both are enabled and I have the usual wireless network icon with a few bars showing signal strength.
Hope this works for someone.