There is one little piece of the puzzle you're missing and that is the role of the Network Administrator. Although I am far from an apologist for Microsoft, in this case Microsoft admitted that a problem existed and provided a patch that works and did so in a timely manner.
So, at this point, if I were a juror asked to hear a lawsuit on this issue, I would attribute the negligence to the Network Administrators that have not fulfilled their duty to maintain the currency of their servers.
Where Microsoft would have a liability would be a case in which it could be shown that they were aware of a problem but suppressed any public awareness and failed to provide a patch. And I believe there are some instances in which that has happened.
So, raise a street mob if you must, but at least pick a winnable case. The CodeRed worm situation is not.
paul