Sounddude:BigGuy:
Just for interest, would OAM ping's not be directed to the ONT?
I don't think that the SRX (or any other CPE) would need to be aware of the underlying upstream protocol! (assuming ATM here!)
Please correct me if I'm wrong.
But to answer your question, I block everything (well almost everything).
It uses ARP :-) So hopefully you are not blocking arp :-)
Hehe... I can assure you I'm not blocking ARP

That would make for an interesting configuration wouldn't it?