Kimmee I am sorry to hear about this, but after 14 yrs with Goofy I tend to agree it may just be your neighbors dog rubs him the wrong way, I have seen Goofster behave terrific with the same dog in a certain sitch, and then behave like a nut in another one, I have also seen her just take an immediate dislike to another dog period. To the point that she will go in her crate and shut the door behind her rather than have me scold her( more like I know you wont like me being aggressive so I will go lie down before you put me in here). I do hope this wont cause issues with your neighbor, and I hope for his sake that he (your pup) relaxes a bit so he can find a great new buddy!We can never have enough fun buddies to spend lazy summer afternoons playing with can we?