1. On the Security tab, click Local intranet, and then click Sites
  2.  In Internet Explorer, click Tools, and then click Internet Options
  3. Click Advanced, and then type: *.domain.com in the Add this Web site to the zone box, where domain.com is your company and top-level domain names(i.e. *.blackbaudhosting.com)
  4. Click Add, click OK, click OK, and then click OK again to close the Internet Options dialog box
  5. Restart the computer
 
 For more information refer to the following article: http://support.microsoft.com/kb/303650