IE8 and Communicator 2005 critical issue

My machine is loaded with Vista Enterprise.
After having installed IE8 (final version), Communicator crashes after
having started (automatically), and IE8 does not work at all. Double clicking
the IE8 shortcut causes the "application stops working" dialog to popup.
Just before that, I had IE8 RC installed and had no problem.

I rolled back to IE7, and try the reinstallation of IE8... Exact same problem.