Nokia Lumia 520 3G blank page

[WPCentral Question]

I have a Nokia 520 Lumia and when I have wi fi on all works great. but when I switch to 3g (I believe the APN settings are okay. I checked them) I cannot browse any page although I have H or H+. It loads about 80-90% and then shows a blank page. So I cannot browse any page.
What might be the problem?
Thanks in advance.