Vista - No network?

Hello,

I have Vista business edition(dutch) installed on my PC.
The first mouth I didn't had any problems with my network. But a few weeks
ago after a reboot I didn't had an internet connection. So I disabled my
network device and enable my network device again.

And my internet was back. But now my network connection is telling me that
there is no network connection...

I can ping the gateway (Router) and the other devices in the network and
vice versa but media sharing is not working...
So I can't share wmv and mp3 files with my xbox360 anymore
I tried to deinstall my network card and rebooting my pc.

After a reboot vista is telling me that I have an unsafe network(don’t know
if this is the right translation from “onbeveiligd netwerk�)but I don’t have
internet….

The IP range that I am using is 192.168.1.X where the router(SMC from 2002)
is the DHCP server /gateway and modem.
Does somebody has the same problem? Because I couldn’t find anything with
search engines…

Thanks for the help!
Kind regards,
Sebastian