Salut am gasit pe net un tutorial ii dau paste aici, I have Nokia Lumia 610.
Even I was experiencing the same.
However I fixed it on my own.
All we need to do is, go to menu by swiping your screen to the right.
Go to Network Setup, you will find this in the menu.
You need not have to download or search for it in Market place.
Just open Network setup, it will automatically search for the network and its required settings.
It will reset the network settings.
Now, this fixes the problem.
Then go to settings, Mobile network and turn on Data connection.
You will be able to browse like never before.
Enjoy! Sper ca merge. Bafta