If you're seeing a blank iTunes Store, see this support article:
If that does't help, try resetting Winsock. This has solved the problem for some people, at least.
1) Click on your start menu.
2) Go to accessories
3) Run the Command Prompt application. For those with Vista or Windows 7, right click on Comman Prompt and choose "run as administrator".
4) Once it opens, type in the following command...
netsh winsock reset
5) hit Enter and it should say something like Winsock reset successful.
6) Reboot your computer and try the iTunes Store again.