I cannot figure out a pattern. If I reboot the machine or add a static route to the router I can then ping it. No other Windows, UNIX, or Linux machines on the network are having this problem. I even upgraded the kernel to 2.4 with no luck. I wiped out Redhat and loaded OpenBSD 2.8.
Same problem occurs.
If I delete the route, then it's fine. Something is sending a multicast router advertisement query. If you want to see this is the case, packet sniff for any packets from the subnet to a multicast address of 224.0.0.1, sending ICMP type 9 messages. Then the problem is either the firewall thinks its a router or another router thinks the firewall is a router and likes to info everyone via the router discovery protocol.