Have you tried Revolution? My vet recommended this and it was the only thing that worked after months of struggling with a flea problem.
It's important to know that fleas don't stay on your dog, they like to settled in dark cracks in your floors, etc. They lay their eggs there and then these will reinfest your dog when they are adults. If you can find diatomaceous earth, sprinkle it on your floors. It's a fine powder and although it smells bad, it kills the fleas and you can vacuum it up afterwards. Otherwise, get a pesticide (I tried Fendona, but hate using pesticides) and spray your house, garden and all your furniture with it. Wait until the moisture evaporates and then vacuum.
You can also sprinkle diatomaceous earth on your dogs, but I personally think it makes my dogs smell very bad (like very smelly dogs, lol).
Once you have gotten rid of the fleas, keep maintaining the status quo by spraying a eucalyptus or tea tree oil and water mixture all around your house. You can also add these oil to your dog's shampoo and conditioner.
I hope that helps
