It appears that the 'ps' command can not manage under heavy load conditions.
I have noticed it during a 'daily' cron job: The 'ps aux' output starts to print
slowly and just hang. I have to kill this unfortunate process to end its
miserable life.
When a shell script executes, a lot of processes start and die at high rate.
The 'ps' command probably makes its way through kernel lists and arrays while
they are changing quickly. Yet, I presume that 'ps' is more than aware about it,
and manipulates kernel data with appropriate care...

Well, let us start to confirm the problem before digging the code out:
Did anyone noticed such 'ps' failure ?

-- Francois Pays