i have quite similar problem... well maybe not that much:
i have all the services running, everything worked fine. i've recently been joining wlan at school (created another connection, i set up another network) and when i returned home i wanted to check how my desktop running xp is faring with the heavy computational tasks i'm doing right now.
and here comes the first 'zonk' - i can't see neither router nor desktop pc (my network = dt with xp and 2k3 and kubuntu, 1 note' w/ vista hp regularly, 2 'drop-bys'). because i played with vista i know the 2 important devices (dt and router) are ok. on vista however i reached the network and sharing center and here goes another zonk:
and no options can be switched - everything is active yet 'apply' buttons do nothing...