I've been getting this issue today and from all my internet searching and such I haven't been able to find a solution to it no matter what I do. My university has 3 networks - one is WPA protected and I have to use my school username/password to log onto it. The other two are unprotected, but are set up so to get to the internet I have to log in with my username/password on my browser before it will connect.
Right now I can only connect to the protected one. The other two are just telling me that Windows can't connect to it. And the secure connection randomly DCs; the actual computer doesn't show a disconnection but the browser stops loading pages for 30 seconds or so, Skype calls disconnect, and if I'm playing a game I DC as well. It reconnects me after a few seconds but it's getting really, really old. So far I've configured my wireless adapter to keep the computer from turning it off, and updated my drivers on the network card. Not sure what else to do that might help, and the problem is so broad that Googling it isn't very helpful.