firewall on the stations has been checked. Further more, if it were firewall it would be all or nothing, right? The clients work for quite sometime, even a day or two after reboot. Then they fall off. Also if it were the firewall on the network, why some machines and not others. Still we have checked the PIX unit to verify if maybe there is a cap on connections, there is not. And even so strange it would typically be the same machines, plus a new one now and again.
Will implement the Kserver monitors though per the suggestion below and update upon seeing results.