This is usually handled best by technical support. You might want to try stps from here:
Firewall, virus-protection, and web-acceleration software can prevent you from connecting to the iTunes Store. You might not be able to connect even if the software appears to be configured to allow full access to the iTunes Store. You can use the MSCONFIG utility to determine if software on your computer is preventing access to the iTunes Store. For detailed instructions, please refer to the following article:
Using Msconfig to troubleshoot conflicts in Windows Vista and Windows 7
Hope this helps.