TCPIP receive problem on Montavista 3.1

I have a communication problem on a Linux Montavista system on PowerPC
IBM405GP processor.
The version of Linux Montavista is : Professional Edition 3.0, based on
a
Linux 2.4.18.
The problem is the following :
The system accept TCPIP/Ethernet connection ; we have 3 or 4 active
input
connections with a traffic of 100 frames by second
(acks/requests/responses).
Sometimes (random delay between 30 minutes and 24 hours), our TCPIP
server
stack doesn't acknowledge anymore incoming tcpip request packets and
repeats
previously aknowledged response packets. The stack is not overloaded
because
all previous request packets have been answered by the application.
After timeout, all connections break down, and the system is able to
accept
other connections and TCPIP packets.

Does anybody knows about such a problem ?

Thanks in advance.