network not recognized

hello,

i have a problem with the network and sharing center (vista home premium).
the tray icon shows correctly that i am connected to the internet but there
is no network shown in the network and sharing center. therefore i cannot
activate the network discovery, file sharing and the other options. but i can
access the web.
i think i might have this problem since installing sp1. my second computer
runs vista business x64 with sp1 and there are no problems.

i really hope that someone can help me.