Taken straighf from the Brightmail Product page on symantec.com
Clients (Internet browsers)
* Microsoft Internet Explorer 6.0, 7.0
* Firefox 2.0, 3.0
Problem solved, you are using an unsupported browser... Go to Firefox, or another machine with IE7 installed. IE8 is so new, that I doubt it will be supported for a while, let alone a patch made just for this from Symantec due to lack of initial market share.