You are familiar with the Zombie instances in Biztalk 2004.  For a background
on zombies
try these articles

Zombies instances are created in Biztalk 2006 also under similar Sequencial Convoy
scenarios. The error description is different.. “The instance completed
without consuming all of its messages. The instance and its unconsumed messages have
been suspended.”

This time around you would think that failed message routing can be used to track
down these failed zombies. Unfortunately, these are not handled by the failed message
handling mechanism. Zombies are suspended as (not resumable). This leaves us with
few options to handle them.. mostly older Biztalk 2004 style WMI event handlers and
so forth

here is one from Darren Jefferd