iTunes for Windows: -3221 error displays when accessing iTunes Store

Error:
iTunes could not connect to the itunes store. An unknown error
occurred (-3221)

Solution:
Some iTunes for Windows users with the McAfee Personal Firewall Plus
installed may display a -3221 error message when you try to access the
iTunes Store using iTunes for Windows. If this happens, try changing
your permission level by doing the following:
Right-click the McAfee icon, point to Personal Firewall, then click
Internet Applications.
Locate iTunes and iTunesHelper in the Internet Applications list.
In the Permissions list, right-click the permission level for iTunes,
and click Allow Full Access.
In the Permissions list, right-click the permission level for
iTunesHelper, and click Allow Full Access.
This should allow iTunes and iTunesHelper to both send and receive data
from the iTunes Store.