Why my consumer sometimes not listening messages?

[Ratha v]

I use older kafka consumer 0.8V.
*Steps*

   - Starting listener
   - Send 10 messages .Listener listens around 4 messages.
   - Send single message. Listener not listening
   - Again single message published. Listener is not listening.

Can anyone explain this behaviour?
-- 
-Ratha
http://vvratha.blogspot.com/