Personal Hotspot under iOS7 with iPhone 5S is not working

Hello,

I got a new iPhone 5S 32GB Spacegray and now, when I try to use it as a personal hotspot, sites are loading forever ( and never show up )

I know that it works, since It did on my old iPhone 4. I have also bought a new Nano-Sim just for this, but it still doesn't work. I can ping google.com, but when I try to surf through the internet, the sites never load up

I don't know what causes this problem, as it did worked before with my old iPhone 4 with iOS7.

My Provider is Vodafone.