Cannot connect to i-Tunes Store.

Hi, I'm Roobin and I have connection issues with i-Tunes Store. Actually, i-Tunes on PC(Windows Vista) cannot connect to i-Tunes Store. I tried Run Diagnostics form the Help menu on i-Tunes. It said that the network connection was ok but I have problem with some "Security Link to i-Tunes" . I don't even know what that means. Also, I tried to fix potentialy firewall issues or else. What more should I do?