I've never heard of seeing flea eggs on a dog!
Could it be tapeworm sections??? Since a dog can get infested w/it if it ingests a flea infected w/it.
I find it strange that I'm reading that frontline doesn't work & that your vets are saying this too. Strange bc I get my frontline from my vet & they work fine for us (knock on wood!). I also have the big bottle style they used to have & it works even better I think. It says in the instruction to spray it all over the pet, but I just spray it along the the back of their necks...just so they don't eat/lick it or anything.