If I remember right (I've not looked at that code in a bit, and my mind is like a steel sieve, only the big pieces stick). EIGRP hello's are marked with tos 6, or the flash, I think it is, and the remainder of the packets are not marked. On the originating router, these high priority packets (not just eigrp packets, other protocols mark their some of their packets at this high level, as well), are placed in a special outbound queue.
So, I suppose the first question is: Why are the neighbors dropping? Is it because they are losing hello's, or other traffic? ARE you seeing hold timer expirations, or retry interval timeouts? If it's retry interval timeouts, then you probably need to do something about treating eigrp unicast traffic in a special way in your policy, so it doesn't always drop, I'd think.
On the inbound side, these packets are treated as a special case by SPD, but it is possible, through user configuration, to cause the packets to drop. I could, of course, be wrong on the marking level, etc., but that should point you in the right direction.
Russ
