strange network problems

[Sebastian]

hi all,
since yesterday I have network trouble with my feisty installation.
I can connect to my router and see that the router is online/connected
but that's about it.
I can't ping or connect to a address outside my network.

The thing is, I haven't changed a thing during the last 3 days, at
least not regarding network/Internet/proxy. Or not to my knowledge.
What I did during the last days (as far as I remember) was try to get
a hald script to run, ran the  software for https://www.osscensus.org/
(you should all participate) and use the thing (surf, email, IM,
audio, video the usual thing).

So I have no idea whats going on or where to start looking...

Please help!

Thanks, Sebastian