Fizzelina - whats the body language of the two of them when your dog is going crazy barking? Is your dogs tail up, ears forward or tail down, ears back - is it dominance or fear?
And the other dog - tail up or down - ears forward or back?
Could be the other dog is sending signals to your dog that say 'im the boss' and your dog doesnt like it - or your dog is sending those signals and cos the other dog isnt listening your dog doesnt like it!
Thanks for the post truthseeker, I'll take a closer look and report back!