I haven't been on Boxerworld for awhile, and I happened to notice this post. My first dog I owned as an adult was a Boxer. A couple months later I got another Boxer. One year later I got a Doberman Pinscher. I think it was a couple years later that I got another Doberman Pinscher. At the time, I had 4 dogs altgether - 2 Boxers and 2 Doberman Pinschers. I never had any problems, but that may be because I prevented them from ever happening. Strange as it may seem, my older Doberman did not want anything to do with the younger one for some time, while the Boxers accepted the younger Doberman. When my second Doberman was first brought to my house, she was already 6 months old, and she was ready to fight with the other 3 dogs, and they were all ready to fight with her. So, I had to keep her separated from the others at first. I can't give all the details of what I did, but I would bring her out with one dog at a time and carefully get them used to each other. Within a couple days, the other dogs accepted her being there. The older Doberman accpeted her being there, but didn't want anything to do with her, at least at first. The younger Doberman also accepted her new family.
At first my younger Doberman did not seem to like any humans other than me. She growled when my wife went to pet her. My 80 pound wife grabbed her and sternly said "I am going to pet you," and petted her of course. Nothing else was needed. She has turned out to be an excellent dog. When I am home, she almost always wants be near where I am.
On November 30th, 2001, my olderst Boxer died. Not too long ago, I got another Boxer puppy. This pup and my youngest Doberman (who might be around 7 years old, I lost track of how old she was) play together constantly. The other two dogs are a little older and don't play with him as much. In fact, the older Boxer is over 10 years old and rarely plays at all. My first Boxer was playful until right before he died. The two Dobermans still play together, but the older one just doesn't play as much.
The pup and the younger Doberman tend to stay close to each other, though at times there may be a dominance battle. The younger Doberman is still the dominant member of the pack, but it looks like this may be changing. Even with that, I have had no problems having Boxers and Doberman Pinschers together.