Problem with some websites

This problem is not really Safari-only, but it fits in this category...

Sometimes, when I try to connect to the university-website (www.uni-erlangen.de), Safari starts to load, and after 1-2 seconds it stops loading. After a minute or so I get the error-message:

Safari can’t open the page.
Safari could not open the page “ http://www.uni-erlangen.de” because the server is not responding.

I have the same behaviour on Firefox and other Browsers. When I start Windows on Bootcamp, it works fine! Also other computers in my network can load the pages. I tried it on different WiFi-Spots, also over LAN, but it doesnt work.

Also the VPN-connection is broken, I simply can't connect.

Here is the output of ping:
*whitebox:~ septi$ ping uni-erlangen.de*
*ping: cannot resolve uni-erlangen.de: Unknown host*
*whitebox:~ septi$*

And here is a screenshot, with the output of the Activity Window in Safari
http://esistaus.de/sr/safari-error.png

This already happened to me in the past several times, and I couldn't access the university-server for several days, and then suddenly everything worked fine.

I tried different DNS-servers but no luck. It seems to be related with some OS-intern networking problem, since every other computer and OS in the same network is able to resolve and load the pages.

I hope you can help me!

Message was edited by: septi