Neutered Male Dog

Question
I have a 2 year old male that was neutered at 6m. We also have a 6m female that recently went into heat,and male is always "humping" her. Recently I found them "stuck together" if you get my drift. I was shocked because I assumed that a neutered dog could no longer do that, and it was safe to leave them together. The two dogs are related so I am concerned. Basically my question is: can a neutered dog become erect and "breed"? Should I be concerned that he was not neutered properly?

Answer
Tracey,
Although I have heard of this before, I have never heard the outcome.  It sounds to me like he has a testicle in there somewhere.  Take him to the vet so you know where you stand with your female, and please let me know what happens in case I ever get this question again.
nancy