I have the same problem. Used McAfee chat to see if they had an answer. The tech support person (sounded like she was in Mumbai) used the Citrix software to run the application remotely and saw the same results before fiddling with my system screen resolution, resetting my McAfee settings, and generally messing up my desktop. She then acknowledged that none of the her attempted solutions worked and suggested that the problem was Microsoft's. That didn't seem reasonable so I tried using McAfee help from Home on Security Center on my XP running IE7; there the window was fine. My interim fix was to copy the help file link from the XP into my Favorites in IE8 and use that way to get readable help.
If McAfee reads any of these forums, they need to address this issue. I see no particular value in hiding the IE functionality when using it for a Help file display; just treat it as any other HTML file and it will work fine. If the user wants to resize the window, let him do so rather than hiding sizing and other IE functionality.
McAfee also needs to provide their customers a mechanism to receive information about unresolved bugs rather than relying solely on the Chat channel; the techs there should offer an email address or some other mechanism by which the user can escalate unresolved problems to a corporate senior support specialist.