DJM,
there is a high possibility that sm evil is bouncing on your web server to build a DrDoS attack against Bell. (If they were stupid enough to generate ICMP unreachable, I think their CPU ressources may be overloaded very quickly.)
If this scenario is correct there is no real danger for ur net, but you have a moral responsability to stop your unwilling cooperation to an evil attack. (U could setup in ur frw a filter IP addy based for few daze)