iTunes Store 10.7 (21) cant brows (white page)

When I select iTunes Store I see only white page,
When the mouse moves to the background given the ability to choose,
When looking for a song you I can't buy it, purchase button does not respond.
reinstall of the system (10.8.1) not fix the problem!
I have 2 computer with same problem.

If you have the same problem on two computers, perhaps you either do not have an Apple ID or a valid credit card to make purchases with?

Yes , I have, I can buy from my iphone or ipad,
The initial problem is: first page is white,
If I'm looking for album I find, but no purchase option.
I added a screenshot

i found the problem!!!

I found the problem
CISCO firewall
if i select "Block Pop-Up Windows "
the itunes Stops working!!!