I also have a problem with one specific dog breed for some reason.
He loves the Collie, He loves 2 Bernese mountain dogs, and a mutt, but he absolutely HATES a foster dog that's a Leonberger (I don't like using that word, but he really does HATE this dog) All the otherdogs were there before he arrived. The Leonberger came after him, and for some reason he hates her! I thought maybe it was the smell of other dogs on her, so we washed her, but to no avail he's still just freaks out at her. I really didn't think it would be a problem especially with her being a female but it is. They are always kept seperated, and I installed blinds on the Leonbergers pen, so that he can't even see her from the house or in his pen. If he does see her, he just barks and barks. I tried introducing them in a controlled setting but it didn'y turn out very well. She is completly submissive to him, yet he doesnt let down at all. Any ideas on why? and why just her?

*sigh