The issue focused on software errors that prevent Windows users from logging on to their computers. By sending Windows messages that contain errors in their programming language, Microsoft programs could crash or hang their clients. http://support.microsoft.com/kb/967074 No proof at all that these kinds of errors actually occur in practice. Yes The expert witness described two widely reported errors that caused Microsoft programs to crash or hang their clients. http://support.microsoft.com/kb/967074 Yes Some experts believed that