I think they're blocking Bitcoin related links. Try some mundane link.
EDIT: I just confirmed my theory: Tiger Woods mmmkay. Bitcoin no mmmkay.
If that is true, it leaves a very bad taste....

I don't use twitter, but I think it is not unrealistic to assume that governments try to influence public opinion at services like twitter through censorship and content manipulation. We don't know if twitter is forced to do this or if they are doing it proactively.
I really hope that this is not true.
Twitter is not government agency but independent company in free market.
If government can press companies over such issues, this is not good at all.