timeout scenerio

i have a problem i hope could be sorted out here.I have an IBM netfinity server which i use to run my telephony billing software.My problem is this;when i ping remote clients, i get intermittent timeouts, infact all clients that are suppose to be offered voice solutions by us, but on pinging these same remote client site with a clone workstations on my network, i get succesful pings to all the remote clients.I had to get another server, this time, a compaq server and the same thing happened.Cansomeone tell me what is going on or is there something with this branded systems.I’m saying all this because authentication service from my clients is never successful and on my own side i have a good link.