what version are you on (and what build - eg 184.108.40.2063)? and this behaviour has been constant across upgrades, etc ?
how much memory do your appserver boxes have and what is the heap setting for the appserver?
do you have the process spawner enabled?
when you say the db may be part of the problem - what do you mean? are you doing cold backups during the night, db is performing poorly? is the db on san or local disk?
can you reproduce this behaviour consistently, or is it sporadic? does the 1st "ALL" appserver hang up as well?