child processes just "waiting for messages"

[ram]

On one of my Centos(5.2) servers MailScanner(4.70.7) processes
sporadically stop pickup of hold mails automatically in the incoming
until I reload
my MTA is  Postfix 

If I do a  "ps  -auxw | grep MailScanner"  
I can see all the processes just like this --
- MailScanner: waiting for messages



The exact same configuration works on all other servers , why does this
server behave strangely. How do I debug this ? 



Thanks
Ram