As your using Internet Explorer, do the following.
1. Open IE
2. Click 'Tools'
3. Then 'Internet Options'
4. Check the 'Privacy' tab to see what setting you have currently set. Click the Default button to reset the settings. As if settings are set too high/sensitive then wont allow you to access majority of sites.
5. Also check the 'Security' tab and click the button called 'Reset all zones to default level'.
6. Close IE
7. Reload IE and see if this as solved the problem.