Windows 7 clearly has some serious networking problems. I occasionaly 'loose' all network connections and rebooting doesn't help but found I can get them back by going to task manager and 'ending' explorer.exe and then restarting it. Hope it works for you.
Are you sure that this is 'no nework access' or is it 'no internet access'? I think that no network access displays a red cross through the tray icon, I could be wrong though. Anyway, it seems that there are 'issues' with Win 7 networking.