Seems your isp doesn't like it.. Or maybe google doesn't like it from where your coming from? Or network between you and google and opendns doesn't like it and drops it. Maybe there are network problems currently between you and them and those packets are being dropped because of min effect on overall traffic, etc.
Could be many reasons for it. Hard to say where the issue is since you do not have control over the other side.. You could try sending zero sized icmp to somewhere you have control over and see if they get there. If they do and answer then you can rule out your ISP blocking/dropping them.
How good is your isp, maybe you can open a ticket with them about it and they can provide some insight?