Delay on voice when Answering call

When a external call comes in and a user picks up he says hello but the caller or the other end does not hear his voice so the user has to pause for about 3 seconds when picking up the hardphone before saying hello.

RING RING-- PICKUP-- PAUSEEEEEE— Hello!

anyone?

PBX Firmware: 1.812.210.57-1
PBX Service Pack: 1.0.0.0

What about the hardware? I suffered this kind on issues with small embeded asterisk machines. It could be a processing problem.

Regards