One thing I have noticed in this thread is the only help being provided is from the community.  NICKSMI seems to be the only Cisco representative responding to this thread and his comments make it sound like it is our fault for not running the latest...

Is the issue with a specific signature being loaded or something else in the package?  I was thinking that if is just a signature that you could use the command line to retire the signature so that it is not loaded and then reset the system.  Any th...

Is there a fix for the systems that have the S601 applied and not responding?

It is an issue with the lastest signature update, refer to https://supportforums.cisco.com/thread/2109620?tstart=0

Having the same issue with S601, reset did not work on either unit.  Glad I only updated in the non-production environment.  Hope a fix comes out soon.