Toolbar Missing in IE8 following Windows Update

The Norton Toolbar went missing in IE8 following a Windows Update. Until then it worked fine. The system is Windows 7 x64, and it's missing from both the 32-bit and 64-bit versions of Internet Explorer.

 

I also have Firefox installed, and the toolbar is alive and well there.

 

How do I reinstall it?

 

Thanks

 

WR