AutoCAD freezes or has very slow startup.

During the application launch, AutoCAD practically freezes and doesn't paint the toolbars.

On a off-line computer (not connected to the Internet), this may be caused by the security communication.

Start Internet Explorer and go to Tools > Internet Options > Advanced tab > Settings > Security. In this section, clear the Publisher's Certificate Revocation check box. Exit by OK.

Now restart AutoCAD.