connection lost when iprohc server is started

Hi, i have followed the tutorial and evertything seems to be working fine. i connected the two pcs through another PC which has 2 NICs and ping works fine. But when i start the iprohc_server, it stops to ping.
ip addr of Iprohc_server eth1: 192.168.42.50
ip addr of Iprohc_client eth1: 192.168.2.5
ip address in iprohc_server.conf 192.168.2.2

i have checked firewall and nothing is blocked. i dont know why the connection seem to be lost when iprohc_server is started. kindly help.