've no problems reaching this website from my Vodaphone/Arcor account.
Not all arcor ip ranges have been blocked. I have a confirmation from mplayerhq.hu for 88.64.0.0/12 and there are some more ranges confirmed by tests.

But on the other hand, I've changed the standard DNS setting in my router recently (currently, I'm using Google at 8.8.4.4 . http://www.omgubuntu.co.uk/2010/09/h...ster-browsing/

If you're able to change your DNS setting in your router easily, I'd recommend trying that. Write down your settings though in case something breaks
Maybe borghal should try it, over here the DNS works fine. IP gets resolved but the servers close connection immediately.

Sorry for hijacking this thread; will stay on topic now