I too have experienced the same symptoms as most on this post and have tried all solutions provided by Microsoft. I could not get more than local access using wireless or ethernet so I was leaning towards it not being just a wireless issue.
I also used the Norton Removal tool and have been able to connect thru wireless to a public hotel network (I haven't been able to connect to anything but a home network for months). I am assuming this coordinates with the timing of when my "free trial" of
Norton ran out and I unistalled it.
Here is a link to download the Norton Removal tool (saves nicely to a flash drive for those who need to use another computer to get to internet):
http://service1.symantec.com/Support/tsgeninfo.nsf/docid/2005033108162039
I found posts dating back to April 2007 with the same issue indicating they had uninstalled security/anti-virus software other than Norton but found a removal tool from the software maker also cleared up the issue.
Hope this helps you, I feel your pain!