Is this a recent issue? If yes, try using System Restore to take you back
to a time before it began. Start\All Programs\Accessories\System
Tools\System Restore.
Do you have a firewall? If yes, check its options to see if one of the
things it's set to block is the source of the issue. If you cannot
determine that way, they turn it off and try. You should clear the IE cache
before trying. Open Internet Explorer, go to Tools, select Internet
Options, on the General tab click Delete Cookies, Delete Files (accept the
option to delete all offline content) and click clear History. If the above
doesn't resolve it check your antivirus and any other security software you
might have, popup blockers, ad blockers, etc.
Is there anything you can think of that you might have changed, installed,
removed, etc. just prior to when this issue began or have you always had
this problem?